Considering how hard it has been, and to some extent still is, to run your own Bluesky instance, the main problem is that it automatically becomes centralised in a way that no open protocol will solve.
If 97% of your users are on one instance it is not a distributed platform. Applying this to mastodon, I am pretty sure most people would consider it a problem if mastodon.social started getting more than 40% of active users (currently at about 15 iirc).
I had it as a mind game for a while to design keyboard layouts that would be optimal for Swedish, German and English (my main languages). I found that you can only get so far with algorithmic approaches. I liked the ones I designed without computer help much better than the one i made with generic algorithms or machine learning, despite being worse on paper. Neither "combos" or distance travelled explained what made the layouts good.
Now, I never used any of the layouts for more than a month or two, but it was still a fun experiment.
I am not sure there is much more to say. I have used an iOS device for many years and "broken and nearly useless" perfectly describes every aspect of the iOS keyboard.
I have always just suspected that it is the same as it was with the lack of t9 dialling. Everybody knew it was awful, but apple just stuck their head in the sand and asked their users to just live with it.
There are many things I dislike about iOS (most notably the settings app), but those are just intermittent annoyances but the keyboards is still so infuriatingly bad.
The reaction at work when I brought a usb keyboard to plug into my phone when I had to write something wasn't "why do you do that?". It was "I have thought about that as well. The keyboard sucks".
IIRC they went for policy based sandboxing with Seatnelt and SIRP. That is pretty darn nice for gui apps, but not very good for things like containers.
I always joke with my American friends (where one can't serve proper haggis or Pölsa due to regulations about selling lungs) that it tastes like freedom.
On the other hand, I could never imagine moving to the US. It seems like such a third world country in so many ways. The amount of households that cant afford a sudden $400 expense without borrowing. The childhood poverty rates. The maternal mortality rate. The traffic deaths (en even worse, the pedestrian traffic deaths going in the wrong direction fast), people dying at work, the fact that you managed to get hookworm BACK, the power grid (I love in a small society in Sweden and I have averages 6 minutes of power outages per year), people being functionally illiterate.
I am pretty sure that would not affect me if I moved there, but I am completely dumbfounded that nobody seems to want to change things. One party wants the status quo and one party seems to want to make things worse.
If 97% of your users are on one instance it is not a distributed platform. Applying this to mastodon, I am pretty sure most people would consider it a problem if mastodon.social started getting more than 40% of active users (currently at about 15 iirc).