Consolidating all of those forums in a single place was nice. I'll credit reddit with that. They also eventually implemented their own image/video hosting after imgur became the very evil it was created to put right, and while reddit's image/video presentation is obnoxious in its own ways it was still an improvement and a valuable feature that they shipped with success.
Other than that, reddit didn't bring anything new to the table. Worse, the things it should have improved on the technical side have been largely neglected. Search on reddit has never not been useless. The UI has always been a mess (and the redesign is so much worse), and mod tools were so bad that third parties ended up creating solutions while reddit did nothing.
The best thing reddit had going for it, and the thing that caused it to become popular in the first place, was the freedom it gave users, but after years of increasing censorship, a total lack of integrity in how they enforce rules, and an unwillingness to implement features users and mods have been asking for a whole lot of reddit was hoping an alternative would come along long before any of this most recent drama.
Reddit had a good thing, but neglect and mismanagement ruined it. They're just coasting on inertia and that slows with every act of petty bullshit users run into. A lot of redditors are just looking for a safe place to jump off so they continue their conversations in peace.