That's not how Apple rolls with the iOS platform. They don't give users the option of downgrading after the code signing window closes. If you choose to update to the latest version of iOS, you have a limited window of time to downgrade. That's how they've operated with the iPhone since the beginning. This is nothing new.
Apple touts the security of iOS, and a big part of that is migrating the vast majority of the ecosystem to the most current standards. If you value stability the most, then you should always wait until the EOL version of iOS comes out before upgrading. But, the tradeoff is that you miss out on the security updates along with all the other new features that Apple wants in front of users (and target to developers).
From what I've seen over the years, more of the random glitches have come from OTA updates. And nowadays, that's how the majority of device owners update. Think about it this way, every time you use an OTA update, a small or large subset of the iOS files get replaced. The list of replaced files gets longer with every successive update, and it becomes more random if you do OTA updates only some of the time, or if you skip some iOS updates. With thousands to hundreds of thousands of files getting replaced, there's a decent chance of something not going right, and there have been past updates where some incorrect files got replaced during the OTA update. That's why for every milestone update and for all XX.X feature updates, I will do the full installation.
All things considered, iOS 14 doesn't have any huge bugs from what I can see. People will gripe about the changes or how certain features work, but it definitely seems that iOS 13 had a rockier launch. Gripes about battery life have accompanied EVERY iOS update, so I tend not to give too much credence to those complaints until after a few weeks have lapsed.