First time seeing Mercury but been watching the business banking space from afar for awhile now (Standard Treasury (acquired by SVB), Azlo (failed), SVB (failed)). I currently run my company on American Express business checking which offers free business checking with a very modest 1.4% yield. However it's FDIC insured not a money market fund like Mercury.
I'm using Chase, which has been kind of a pain to adapt to our needs, but it's JP Morgan and won't be going anywhere.
Government backed money market funds are safer if you have over $250k (well, were before SVB, now the limit is up to who you've influenced)
You can be fully insured on Mercury. They spread your money out at multiple banks.