Absolutely, biggest myth in the sport.
Back in the day if you wanted to learn striking you had to find a striking gym (boxing, MT, kickboxing, etc). You were going to become proficient in that art. Same with BJJ, wrestling, etc. If you wanted to become good at MMA you were forced to travel to different gyms and be good at that individual aspect.
Now you got cookie cutter gyme offering everything but the instruction imo isn't as good. I train at one of the better BJJ gyms in Chicago. They offer boxing and MT there too but imo their striking instruction falls severely behind the grappling instruction.
Now I know I few places like Portage Park MT has high level MT and kickboxing instruction but they offer BJJ classes to. You think their BJJ classes are on par with my gyms BJJ instructions? You'd be out of your mind to think so. And I would be out of my mind to believe we have better striking instruction than Portage Park MT.
I think when people say "evolved" they mean well rounded. That I can agree with. But it's all cookie cutter nowadays. But if they say the striking is better nowadays or the grappling is then I call BS.
Jan, who is from the old generation, just won the LHW title over a new generation guy. Knocked him senseless.
What I do think that has consistently improved is nutrition and training methods. You don't hear about gym wars anymore like we use to. Hell people, like Robbie Lawler when he was champ, don't even heavy spar anymore. They realize the risk/reward isn't worth it.
Anyway I'm just rambling now. Just my 2 cents. Point is back in the day you had to learn boxing at a dedicated boxing gym and BJJ at a dedicated bjj school. Now we got all in one that seems better but in my opinion isn't.