It depends what you mean by "problem". For example, Reuters presents it this way:
In an interview with ABC News aired Tuesday, Hunter Biden said in retrospect it may have been poor judgment to join Burisma’s board while his father was vice president, but added: “Did I make a mistake based upon some ethical lapse? Absolutely not.”
Biden, in the interview added that he didn’t discuss his business dealings in Ukraine with his father, other than one brief exchange in which his father told him “I hope you know what you’re doing.”
Lutsenko, who succeeded Shokin as Ukraine’s prosecutor general in 2016, took over a tax investigation into Burisma before closing the case ten months later, after the company had paid a settlement in relation to the tax investigation.
The former prosecutor said that any issues Burisma did have were not related to Biden. In addition to the closed tax investigation, Ukraine authorities opened an investigation into licenses awarded to Burisma and a separate money-laundering probe into founder Zlochevsky. Both of these have been re-opened in recent months, but neither relate to the period after Biden joined the board.
So basically, besides Hunter's poor judgement (that Kent has described as an "appearance of a conflict of interest") the MSM says that the Ukrainian investigations into Burisma were not into any matter that Hunter was personally involved with. I think that the witnesses in the impeachment hearings insofar have backed up this latter viewpoint as well (Kent included).
On the other hand, Vox is more critical on the "poor judgement" part calling it "a kind of soft corruption":
Hunter Biden isn’t a natural gas expert, and he’s not a Ukraine expert. But he was son of the then vice president of the United States. And that’s why he was paid hundreds of thousands of dollars to sit on Burisma’s board — among others. The New Yorker’s investigation, which predates the revelation of Trump’s call with Ukraine President Volodymyr Zelensky, put it well:
Several former officials in the Obama Administration and at the State Department insisted that Hunter’s role at Burisma had no effect on his father’s policies in Ukraine, but said that, nevertheless, Hunter should not have taken the board seat. As the former senior White House aide put it, there was a perception that “Hunter was on the loose, potentially undermining his father’s message.” The same aide said that Hunter should have recognized that at least some of his foreign business partners were motivated to work with him because they wanted “to be able to say that they are affiliated with Biden.” A former business associate said, “The appearance of a conflict of interest is good enough, at this level of politics, to keep you from doing things like that.”
It wasn’t illegal for Hunter Biden to take that job. But Hunter Biden himself has admitted it was “poor judgment.” It’s reminiscent of nothing so much as the $675,000 Hillary Clinton took for giving speeches to Goldman Sachs: not illegal, but a kind of soft corruption that voters find loathsome.
Clinton and Biden both make the same argument: The money — in Clinton’s case direct, in Biden’s case to his son — didn’t affect their decisions. I believe Biden on this. But these are huge sums and represent a kind of DC back-scratching and influence-trading that voters dislike. Getting paid hundreds of thousands of dollars for doing basically no work is a rare gift, and the cost of accepting that gift or of letting a family member accept it is it can be used against you in a future election.
None of this is news to Biden. As the Intercept’s Ryan Grim documented, Biden has faced attacks for decades over not just Hunter’s work, but his brother James’s efforts to cash in on his name, so he knew this was a vulnerability long before Burisma. Biden’s answer here seems to have been to create a personal firewall about the topics he’d discuss with Hunter. “I never discussed a single thing with my son about anything having do with Ukraine,” he said. “No one has indicated I have. We kept everything separate.”
I don't know why you think it should be called a "major conflict of interest" though. Major conflict between what interests?
Actually, The Nation (which more left-wing than Biden or even Vox perhaphs) did call it nearly in the terms you want "a conflict of interest ipso facto", and back in May:
Joe Biden’s Conflict of Interest on Ukraine [...]
The problem – indeed, the only reason we’re discussing this three years later – is that Hunter Biden should’ve never joined Burisma’s board to begin with. His decision to do so displays a lack of judgement on the part of both Bidens, one that is relevant now that Joe Biden is running for president.
[...] What services Hunter provided to Burisma remains unclear, but at one point he was making as much as $50,000 a month. That, in itself, should’ve raised red flags. Indeed, it had.
Hunter Biden joined Burisma in 2014, two years before his father gleefully pressured Ukraine to fire Shokin. That inherently problematic decision was immediately covered by Western media, including the BBC. It was further highlighted by a 2015 Times editorial, which stated: “It should be plain to Hunter Biden that any connection with a Ukrainian oligarch damages his father’s efforts to help Ukraine. This is not a board he should be sitting on.”
And yet, the Bidens seem reluctant to address the situation: both men told the Times Hunter’s involvement with Burisma wasn’t an issue because they don’t discuss personal business dealings. (If this sounds familiar, it’s because the Trump family claims the same thing about their business interactions.) Unfortunately, that’s not how conflicts of interest work.
The vice-president’s son landed a questionable – and lucrative – sinecure in an economically unstable nation that played a key role in US foreign policy and was heavily-dependent on Western aid. This created a conflict of interest ipso facto, regardless of intentions.
The same article in The Nation does criticize later on the more lenient conclusions in two other articles, one in the Washington Post and another in Mother Jones, respectively.
And (needless to say) on Fox News, Hunter Biden gets no quarter with articles reporting Trump's view on the matter extensively:
Hunter Biden's questionable past and business dealings could undo dad's bid for White House [...]
What's true is that Hunter Biden has become a punching bag for the White House and Trump's closest allies. The 49-year-old's controversial decision to accept a high-paying position at a gas company in Ukraine with little to no experience has become the backdrop of a whistleblower complaint against Trump and is reshaping the 2020 presidential race. Trump has repeatedly accused Hunter Biden of ethical lapses and profiting off his famous father's last name -- something Trump's own children have been widely criticized for doing.
Earlier this week, Trump tweeted, "Where's Hunter? He has totally disappeared! Now looks like he has raised and scammed even more countries! Media is AWOL."
The social media hits against the Bidens made by a sitting president have been relentless and somewhat shifted the focus of the investigation against Trump to an attack on Hunter Biden. [...]
But in the non-opinion articles, Fox dos sometimes point out the lack of evidence for some Trump allegations:
There have also been concerns about Hunter Biden's dealings with BHR (Shanghai) Equity Investment Fund Management Company. Trump and his personal attorney Rudy Giuliani claimed that Biden used his father's position as vice president to secure $1.5 billion in loans for the Chinese private equity company, where he was a board member. There is currently no credible evidence to support the theory.
So at this point it comes down to what part of the press you want to call the MSM. It's probably unsurprising that the center-left media has been less critical of Hunter than either the more outwardly left-wing or the right-wing parts of the media.