The difference is that Fortnite has all those things and somehow manages to be absolute bland-ass.

Fortnite lacks a central theme compared to TF2, it's just random, generic cartoonieness. Admittedly, TF2 has slightly ruined it's artstyle through cosmetics items added over the years, but it still retains its retro 60's spy/evil genius vibe. Also, TF2 boasts a cast with distinct personalities while Fornite has just… dance emotes and Thanos?