I think you’ve hit the nail on the head a bit, Reddit users were for all intents and purposes anonymous - you’d find usernames you recognise but it’s among a sea of thousands of others, and the posts would all blur themselves into one. By and large, you go into a thread on a topic, not because Person X posted it, but because it’s a topic you want to read about, and you upvote a comment because you liked it rather than because Person Y posted it.

Twitter is all about who you follow and you curate a follow list that matches what you want to see, and by return you engage with the people who engage with you. If the people who you’d want to follow on a replacement for Twitter aren’t there, or nobody can or will engage with you, it’s a shitty replacement for Twitter for your purposes. This is especially true with Mastodon, whose model is that you only see posts from the follow lists of people already on your instances, so if it starts off sucky then absent some external force, it stays that way.