Fully agree.
I’m one of those people who migrated to tumblr after the Reddit exodus (tbh I did have tumblr beforehand, but my usage increased a lot when the API bullshit happened). After using it for around 10 months I’ve come to the conclusion while yes, it is good for fandom related content, memes and some other things it’s simply no replacement for reddit (it’s actually more of a replacement for my fandom instagram to me). Yeah you can follow hashtags or topics, but tumblr is too niche of a platform and a lot of the topics I care about the average tumblr user doesn’t even think of, or at least not to the extent I do.
If you want a reddit replacement Lemmy is simply your best option. If you want a Twitter replacement then yeah, go ahead and use Mastodon.