Repos aren't exactly bond buybacks, they are more like temporarily loaning cash in return of a treasury bond. It has a neutral effect on the Fed's balance sheet. So overall, the money supply stays the same. It does help keep liquidity available since few banks/Institutional investors keep any significant cash reserve which is usually okay, but can be dangerous if there is a sudden run for cash.

And if anything, the Fed interventionist policies are a good sign. You could argue that it is bad for the Fed to intervene in the economy during bull markets and periods of economic growth, but for situations like these the Fed can be a huge factor in avoiding a collapse of credit and liquidity. If credit stays available there is little reason to believe the economy will be affected by anything more than what the virus directly causes. So structural collapse of the financial system/job market like that of 2008 is unlikely as long as credit is readily available to corporations and banks.