Some reasons why a CDBC (be it called "digital rouble" or more improperly "crypto-ruble") might not actually be that effective at bypassing US sanctions-- basically because simply using it will raise red flags and possibly attract US investigations and sanctions:
the ability of a crypto-rouble to help Russia evade U.S. sanctions is limited. Prohibited transactions would be continue to prohibited regardless of the means of exchange. Theoretically, it would be harder to get caught if you’re using currency that cannot be detected by U.S. regulators. But it is unclear just how many world financial actors would accept Russian government crypto-rouble surveillance, in exchange for protection from scrutiny by U.S. financial regulators. For this reason, the primary user of the crypto-ruble might be the Russian state itself.
if a crypto-rouble were to be issued by the Russian central bank (or even by a commercial bank in Russia), then the very existence of that platform would lend itself to detection. Although the currency itself could be secure, exchanges denominated in the currency would likely flow in more predictable paths than standard crypto-currencies. Thus it would only be a matter of time before U.S. enforcement agencies could identify red flags and investigate potentially prohibited transactions.
An executive at Gazprombank, the state-run bank that is subject to U.S. sectoral sanctions, acknowledged that “[c]rypto isn’t the answer in a quick way.”
As was actually noted in the OP's article, both China and Russia have parallel systems [relative to Swift] for their own banks (CIPS and SPFS) already. The real issue/question is: why would some other country [not] use them. The Wikipedia article on the latter cites Russian state sources that interoperability deals have been reached with China, India, Iran, and some other coutries and that 15% of Russia's internal transactions use the system. But it's a little unclear how widely adopted it is outside. (The Wikipedia article on China's system lacks concrete data.) But for many other countries, the question is basically: why bother?
A somewhat subtle aspect here is (as explained in the CIPS article) is that the system itself only sends orders, but that actual settlement happens through correspondent accounts. And these are also on the target list of US sanctions.
As Wikipedia explains the concept:
A bank will typically require correspondent accounts for holding currencies outside of jurisdictions where it has a branch or affiliate. This is because most central bank settlement systems do not register deposits or transfer funds to banks not doing business in their countries. With few exceptions, the actual funds held in any foreign currency account (whether for a bank or for its customer) are held in the bank's correspondent account in that currency's home country.
So you couldn't exchange (bank) dollars in the usual manner if the US government puts your banks on their CAPTA list. (I'll also note that this list is rather new, and hasn't been used extensively insofar. Presumably it was added in view of possible bypass of Swift as by using different order messaging platforms like CIPS/SPFS.)
So you'd either have to pay with dollars in suitcases as Iran started to do and I think still does now to some extent (even with Russia) , or you'd have to use a different currency altogether... which gets to the bigger issue of whom accepts what currency as payment, which Ryathal's answer addresses already.