I think your question needs a bit more specification, because you have not written from whose point of view might it be a problem. I am just viewing your elections as a foreigner, but here my my views.
For the current president Iohannis it is very much the strategy not to have a direct debate. This is because he is leading the polls significantly, and going into a debate may raise Dancila to his "level" in the perception of the voters. He instead behaves as someone above the level of Dancila and he wants to keep this image. He also expects that voters of Dan Barna will support him without a debae in the next round and probably also some voters of PMP as well as a few Hungarians.
For Dancila it is indeed a problem not to have a debate with Iohannis, and the same was true for the other candidates before the first round of the election. That is why she is asking repeatedly for such a debate.
For most of the supporters of Iohannis it is not a problem that they do not see their favourite candidate in a debate, because they do not support Iohannis for his exceptional debating or rhetoric skills or his explicit political plans for Romania, but rather for his image. He presents himself as "the European cadidate", someone who has the best connections with Western Europe/Germany. They vote on this image rather than the results or resolutions of him.
On the other hand, most of the supporters of Dancila (PSD) come from the less educated people who are usually not that much interested in such political debates, because they again often vote following the image they associate with their candidate/party.
For voters who have not decided yet the lack of a debate can be some problem, but I guess Iohannis calculated form the polls that it does not worth for him to take a risk for this group.