The issue is rent seeking behaviour that spawns across our current capitalist systems. (No this is not a rant against capitalism or a pro communism statement, just a problem description)
Basically our current capitalism system incentivises not "value creation" as an utopian version of capitalism would incentivise, but actually "rent seeking" aka "build a moat, capture users". Everyone is after guaranteed recurring revenue, and it is done by shackling you to the service being provided, check "right to repair" issues, check compatibility in software ecosystems.
Someone builds a very good product, people migrate to it, they pay you money, maybe even pay you to keep using it (subscription), but how to you guarantee that they are not switching to something else? Add as much lock in as possible, or make it free so you can sell user data/put adds. All of these are not connected to the quality or "value" you are providing to customers, but rather into ways of keeping your moat / stop competition from rising.
tragedy of the commons (and similiar issues) means that we can never have the utopian capitalist/free market world. Regulation is always needed to avoid such issues, but at the same time regulation can also backfire and instead create these moats/rent. The utopian Capitalist world, just like the utopian Communism cannot exist. And the end of the day, there can never be purity, and systems need continuous engineering/maintenance effort.
In your example, TikTok want you to use the app, website is not a priority, they can't gather as much info there, it just exists so that someone using the app could send a video to someone without it. Also, it still needs a ton of bloat to still get as much info from you as they can. So, with less resources and with still wanting to spy on you as much as they can, it's normal that the video player might not work in all browser/OS/device combinations.
Same shit across every product, now add things like speed of delivery of new features or new ways to spy being more important that performance/quality, and you get trash software.