I don't know about so-called "dudebro" gamers, but I do remember a lot of kids playing beat 'em ups in the arcades back then. Konami brought in a lot of young kids with their licensed stuff. I mean, if you were a kid back then you loved the Teenage Mutant Ninja Turtles cartoon. So when you saw a ninja turtles game in the arcade, that's what you played. I don't know if there were a lot of nongamers in arcades back then (aside from kids who maybe weren't gamers, but just went there to play Ninja Turtles or The Simpsons). I don't think gaming was super mainstream at the time, at least not on the same level as it became with the Playstation.
However, like someone else said, you could find arcade machines everywhere back then. So I suppose a fair share of non-gamers played quite a few beat 'em ups back then, even if they never visited an arcade. I mean you could go to the supermarket or pharmacy and find an arcade game back then. They might have attracted some non-gamers or non-nerdy people, along with the young kids that flocked to Konami's cartoon based beat 'em ups. However, I didn't personally notice many non-gamer types and older gamers ( teens to college age) hanging out in arcades in my local area until Capcom's comic book inspired, 2D fighters really hit it big like Marvel Super Heroes, X-Men vs Streetfighter, or Marvel vs Capcom. The closest thing I ever got to what you might call a "dudebro" experience is when I had a close call victory over someone in Marvel vs. Capcom and heard a couple of guys behind me all yell out like they had just seen a touchdown on TV
All my experiences are based on the local area I lived in back then, which was Scranton PA. So take that for what it's worth. I have no idea who was playing beat 'em ups throughout the country in arcades. I never really had friends to play
console beat 'em ups with, just didn't have many hardcore gamer friends back then. So the much talked about co-op experience is something I didn't get with a lot of games unless I went to a local arcade. The SNES always seemed to have more 2D beat 'em ups than the Genny back then, but I still had lots fun with games like Comix Zone and the Streets of Rage games. I would late discover some other cool beat 'em ups on the Genesis.
As for beat 'em ups being all the same or lacking quality, I did an article focusing on a variety of beat 'em up games, mostly lesser known, more obscure titles that will hopefully show the amount of variety and depth to the genre. I don't know when Racketboy will put it up though. It's basically the beat 'em up equivalent to Ack's Hidden Gems of the 2D Fighter article. I wanted to cover 3D beat 'em ups too, but the article was big enough just with the 2D stuff. If you want to talk about beat 'em ups all being clones, look into some Beats of Rage games
A note on co-op, it's a huge part of the genre, but there has always been a thriving community of hardcore gamers who love going through a beat 'em up solo, and doing their best to beat in on one credit, or one life. That's when you really see the depth of a good beat 'em up. Too many people just credit feed through them or rely on a group of friends to get them through the game, then complain that the game is too simplistic or easy. On the flip side, you have your weaksauce gamers who can't get through a game solo without credit feeding and bash the game for its difficulty(i.e. most modern reviewers when an old school beat 'em up gets released on Xbox Live Arcade or PSN)