That’s fair, and that’s also why companies like Boeing traditionally let two different companies implement the same spec for their planes’ computer systems (the ones with failovers at least); that way, the exact same bug couldn’t knock out the entire system. Well, it did once, but it helped in other cases.

However, based on the statistics I can find, alternative software is rather insignificant in terms of market share. Mastodon has ten times the amount of users its next competitor has. Unless you count Threads, I guess, which still blows the rest of the Fediverse out of the water at the moment.