I do think people are much happier than they were 20 or even 10 years ago, largely thanks to the increased joy brought by better apps. Can that continue until people are "overwhelmed with the pure bliss of being alive"? No clue, doesn't seem likely, but it's certainly possible.
E.g this study: http://journals.sagepub.com/doi/full/10.1177/216770261772337...
Suicide rates increasing because of too much bliss?
Once you start scrolling there, it is very difficult to stop, and I have tried it, but I don't think at least for me, it would add any actual value to my life even if I can't stop myself from using the app.
There's other entertainment, that I would think is more healthy, meaningful and can improve you as a person, so any time spent on Tiktok, I think is straying away from that other type of media.
So Tiktok definitely has impact, but I don't see how this impact is more positive as compared to say reading books or similar, which could potentially also provide infinite entertainment, but I also improve your brain