Twitter is very much a walled garden and is in that sense rapidly becoming more so, especially because Elon Musk is dreaming of making the Twitter app into the 'everything' app that will be a platform for all your comms and commercial transactions. AOL next gen.
It's also not a "fair" comparison because twitter was born before smartphone penetration and the "mobile first" thing. They launched on the web first, like Facebook, and probably would love to wall things off more and lock out the web, but can't now. (Though Musk clearly made an effort a couple weeks ago by requiring log in to view any tweets, he's had to partially roll that back, though not fully)
When I went looking at any of the various new social network startups that have tried to get into the market all of them -- except the fediverse/open-source/hacker type projects -- were mobile only, even some after years of being on the market. Clearly highly motivated to keep a mobile-only moat around things.
