I disagree that raids today are more difficult. They are massively undertuned in some circumstances . mythic archimonde can be killed with 0 legendary rings, while most people doing mythic today have full upgraded legendary rings and 2/2 upgrades.
The classes themselves are braindead and the pruning has gone way to far. Arms warrior is just as braindead to play when your killing mythic archi as it is the rest of the time..
I personally got multiple 99% parses in heroic BRF as a survival hunter, completely braindead spec to say the least.
In vanilla you had to worry about spell ranks, threat management, mana management, you had to be careful with your pulls, you had to CC, you had a massive amount of preparation that was required, a massive setback on wiping in the form of a long run back / trash to clear, aswell as fights that were extremely challenging mechanically ( 4 horseman is honestly a hard to execute fight, even by today's standard's. )
I would also like to point out that just executing and perfecting your strat / mechanics doesn't feel like a compelling/ difficult challenge. I will always be able to execute the fight, but if the tuning isn't there ( which it's not ) , then the raid will NOT feel challenging.