There are a very small handful of Safari extensions, and most of them are mediocre at best. Lots of Ad Blockers and privacy-related apps and not a whole lot more.
Yes, that's my point. And out of the 100s, they're mostly the same 4 or 5 types (ad blockers, privacy protection, password management, and shopping). Firefox and Chrome have hundreds of thousands ranging from popular to obscure app integrations and a ton more.
Safari add-ons were much better before Apple forced developers to create a separate app just to add a small feature to Safari AND distribute exclusively through the app store.
I'm normally behind Apple with the direction they take with these sort of things, but Safari extensions are not one I particularly like.