There is no Constitutional requirement or law forcing any presidential candidate to release their tax records. It shouldn't be an issue. If a candidate wants to release them, fine; if not, fine as well. Besides, how can one tell the tax records a candidate releases is actually the tax record submitted to the IRS?
The truth of the matter regarding debates this election season is - Democrats are scared to death of Biden debating Trump. They know the more Biden talks, the more gaffes he makes. He also has a a strong tendency to take credit for things he did not do. Biden doesn't stay home to protect himself from COVID; he stays home to protect himself from his own mouth. The left made fun of Trump for going into the bunker. What the hell is Biden doing right now? His bunker is his home. Do we want a leader who is afraid to go out into public, who stays home because he's afraid he's going to get sick? What the hell kind of signal is that to the people when you claim you can rebound the economy? "Hey folks, stay home so you don't get sick."
The Democratic Party is such a joke.