I'm running my ATV 4K 2017 on ethernet without any issues. I very rarely have to restart it for any reason, and never due to poor bandwidth performance. I've also used it on Wi-Fi and it had no issues.
About the bugs, yep, lots of those. Apple is notorious for bugs the last few years, and that is within all of their OSes. They really need to get that under control.
What I notice though is that whenever Apple releases a significant update to tvOS, it often takes some of the app developers a few weeks to get the kinks worked out. Although it could indicate bugs, it probably has more to do with new features that were added, and with new ways of handling the code that were introduced. Hulu seems to be a good example. Ever since 14.4 Hulu has been really bad at losing the streams and other issues. When Apple changes the code, the app developers will need to update their code to work with it, and that simply takes time.
In my case, I rarely seem to have issues streaming CuriosityStream, BritBox, YouTube, Netflix, Disney+, NatGeo, or even Amazon Prime. Philo and Hulu have been issues on and off. Philo got so bad that I cancelled it and went back to Hulu for streaming live TV. I seem to only have major issues with the live TV streaming apps. The on demand streaming apps are usually okay.
I still suspect that the Wi-Fi issues the OP is having are due to sharing the internet service with someone who has total control of the system. You can have a fast internet service, but when it gets shared with multiple users it can suffer issues. There is only a finite amount of internet bandwidth entering the building, and it gets shared between multiple users. Whoever controls the keys to the kingdom is going to rule in such a case. Find a way to escape the serfdom, and set up your own internet service wherein you are the king!