Of course, there will always be someone who won't care about their users, it's inevitable. But knowing how sausage is made, there are different trade offs when it comes to authentication...
I was at google before here, and things there are much much more stricter to the point where even an internal employee cannot do much help for themselves [1] as it happened to me with my own account. That's also not good. Things do get better, but they probably have different trade offs.
I am not sure if "scale of product increases quality will decrease". I remember twitter fail whale, and seeing it constantly, I remember android bugs from google, I somewhat remember fb's own issues (but this part is fuzzy as i have been a very light user - twitter is more my jam vs fb). Also early on internet was cleaner, spam and fraud was less, crypto money scams were nowhere to be seen at the time. So i'd say things actually got much better, maybe "attention to detail" diminished, which i guess i could see.
[1] https://news.ycombinator.com/item?id=31391843