While I am not in favor at all of "big tech", I must say Gmail has been rock solid for the almost 20 years I've been using it. I would consider Gmail a truly reliable service. Not all "big tech" is bad per default.
The ONLY thing I find annoying about Gmail, is that when you use it via the Gmail app on Android phones, you are also automatically logged in to other Google services such as YouTube. When I log into a webmail account, I prefer to be logged in only in that webmail account. However, when I log into Gmail via a browser on my laptop, it does not log me in automatically into other Google services, so alltogether it's OK
Also, Gmail supports Yubikey, which I consider the best form of 2FA. Granted, Outlook supports it too, but I don't know if other huge providers do so.
The spam filters of Gmail are also working very good, I rarely had any spam in my inbox, and very rarely a reliable email ended up in Spam per mistake.
So big tech or not, Gmail is a very solid provider in my opinion.