Even if the Biden agenda is genuinely unpopular with their voters (doubtful but ok), spending months talking about the Failed Biden Presidency is going to be much more damaging to them.
"I"m a Democrat who hates Democrats" has long been an electoral strategy for some, and while you can point to a couple who manage to make it work, I do not think the electoral outcomes of the past 20 years show that it is a particularly winning one. Sink or swim together, mostly.
And it's one thing to set yourself apart from Those Other Democrats when they're out of power, but "we run the government and we are fucking awful, vote to re-elect me!" is pretty stupid.