The fact that free apps (or hacks, like Revanced) are better usually has to do with the incentives driving their development.
For services like YouTube, Hulu, etc., the developers are doing it as part of their job, with overall direction set by the company. They may not agree with the overall direction, or may not even use the product, but they have to do what the company says so they can keep their job and get paid.
On the other hand, for small independent projects, the developers use it themselves and are building it based on what they want plus community feedback. If it’s open-source, other developers can contribute features they want to see, too.
This is why pirate video apps (both old ones like Popcorn Time, and also newer ones like Syncler, Weyd, CinemaHD, etc) generally have far better UX than the “official” services - it’s developed with love, not with a “get this done so we can go home by 5” mindset.
There’s also some things the official services don’t even do. If you want to stream a movie in full quality (like a Blu-ray remux), the only way to do it is via something like Weyd plus Real-Debrid. None of the official streaming services have videos this high quality. Missed opportunity, IMO.