Not really. In terms of engaging with posts, oh my god, absolutely it's worse. Twitter and its clones suck when it comes to engaging with things people post (but Mastodon at least makes it a bit better by increasing the character limit). But there's just something different about following a hashtag versus following a Lemmy community. Like for example, when it comes to getting highly detailed, up-to-the-minute news about things, Mastodon beats Lemmy every time. Additionally, I can see people's random, one-off takes that wouldn't really warrant a post on Lemmy.
I would argue too that it's not even true that you should just be focused on following hashtags, but rather that you should be trying to do both.
To me, Lemmy is the type of place I could kill two hours; for Mastodon, it's maybe 15 minutes, but that doesn't make it inferior, just a different use-case. It's pretty apples-to-oranges.
See, I already know who I want to follow. I want to follow Nintendo. I want to follow Game Grumps. I want to follow my local pro wrestling indy. I want to follow MXRPlays.
But none of them are on the fediverse. Although, Andy Richter is on BlueSky. So that's something......I guess......
If you start following hashtags, then you find interesting people. There are also curated lists that you can sign up for. That will introduce you to a lot of new content.