I used to use both Twitter and Reddit (until they both succumbed to an Eternal September of their own, in my view, although for different reasons), and at least to me they serve very different purposes:
Twitter was great for following the updates of a given person/company/group etc. It allowed me to keep up to date with various topics of interest (cryptography, engineering, my city's public transit system etc). The 140 character limit was always a red herring, in my view: People can just link to their blog or start a thread (which I can both easily follow and ignore).
Reddit was more useful for researching and discussing a given topic. Discussions are way more meandering, and the tree-based interface made that both acceptable (whereas spamming somebody's replies would be considered rude on Twitter) and ergonomic.
In that sense, Reddit was always the spiritual successor to self-hosted bulletin boards, in the same way that Discord has replaced IRC for many groups. (What makes me sad is that it's now seemingly also replacing discussion boards, which sucks because it's not anonymously searchable at all, but that's a different complaint.)
In that way, Reddit seems like a very low hanging fruit to decentralize: Its predecessor already was decentral, in a way! In contrast, there was never a successful decentralized microblogging service before Twitter (and no, RSS doesn't count).
> I hate algorithmic feeds. I just want to see who I follow and no other suggested or promoted stuff :)
That's very fair! I believe this is what ultimately got me quite hooked on Twitter, but in the long run has made me very unhappy while there and prone to doomscrolling.