I agree with you that Classic’s class design lead to very limiting gameplay for a lot of people, but:
You’re arguing a community problem versus a gameplay problem. On the one hand, you ‘can’t’ use a build because you can’t get into certain groups.
On the other, you literally can’t use a certain build because it does not exist.
I feel Classic is what had the design flaws. Classic is about playing a class. That class typically had 1 role/“spec” that was worth playing.
If you were a hybrid, you were a healer.
If you were a tank, you were a warrior.
Classic had the worst class balancing/design in WoW’s history. Sure. It had plenty of “flavor” spells. But gameplay wise? No.
The guidelines of General says the opposite. Right at the beginning it stares that it is for talking about all aspects of World of Warcraft. Classic definitely qualifies. Would it be better if it was in Classic? Yeah but people should stop acting like people are doing something wrong by posting Classic discussions in General. Because they are well within their rights to do so.
If enough people disagree, talk to Blizzard about changing the guidelines for General.
It is incredibly punitive at end game of Vanilla to have to swap from ret which you want to play to holy that you are forced to play.
The penalty in Classic was gold and the cost to have 40 people be forced to repot/flask/elixer/resist because your guild wants to carry a class that is just broken.
WoW’s population took off in TBC because they fixed obvious mistakes in class development for Vanilla. If they release a TBC server then I will play on that but I like Paladins and I refuse to be relegated to being a healer if I want to play the game.
The streamers who are pumping up Classic are making a CRITICAL mistake that will lead to a severe backlash when people call for changes that are never going to happen.
Blizzard is moving these threads over to classic - which says yes they are posting in the wrong section. All they are doing is wasting people’s time.
People can’t be so dense not to understand that they created that section for a reason.
And no ones’ forcing anything or talking about rules, the person pointed out he’d get a better and more meaningful response in the Classic forum where there are people who know what they are talking about.
Lots of people are starting to get indigestion seeing these Classic threads pop up like rabies. You just can’t get rid of it anymore… 
Everyone is acting like the OP is saying he wants a return to Classic. That’s not what he said at all. He posits that having class design now, like was back in Classic, only BALANCED PROPERLY would be a good thing. And that it might even include the old talent tree system. I happen to agree with him. Other don’t. But please don’t say he just wants Classic back.
I like the idea of the old talent tree system, I remember the same thing in D2 and D2 LOD. I was able to mix and match talents BUT to a very limited point… there was always a set build that was optimal, picking anything else really put you at a disadvantage.
Same with the old tree in WoW. And balancing it, is extremely difficult I’d imagine to make it so there isn’t just some cookie cutter build.
You’re super wrong. General is the catch all for whatever someone wants to post as long as it’s connected to WoW. Try this…if in the title it says “classic”, don’t read it.
This is from Blizzard , " Welcome to the General Discussion forum! This forum is here to provide you with a friendly environment where you can discuss all aspects of World of Warcraft with other players.
Even then I feel that those classes had more charm and RPG elements attached to them. For me it felt like I was playing DnD the game back then.
Even if it’s clutter I loved having to feed my virtual good boi/gurl, having to always stock up on ammo and even having the dead zone. I’m looking forward to the experience.
General discussion is for discussing all aspects of WoW, friend.
Not when there is a forum to discuss the topic at hand.
Classic: only one of your specs is usable and the rest are trash
BfA: all specs are fully fleshed out and usable, though balance issues lead to some over performing and others under performing
While this is true, it also misses the fact that Classic designs had a lot of flavor. This is also where a lot of the jank came from, but:
The later expansions perfected upon Classic’s initial design. I believe the OP wants to see a return to that, the perfected ideal of that RP-heavy class design Classic had, rather than Classic class design period.
I think, OP, you made a mistake by putting ‘Classic’ in your title at all. People do love to fixate on the title of an article, and a post on a forum is no different.
Let’s not pretend you would have also said this if in the comparison the OP made BfA came out as being better than classic 
If you don’t like chores why do you play BFA? BFA is quite literally an expansion of “do your daily chores for a chance at bis loot”. I never understand how people think classic had more tedious chores compared to live. World and daily quests are driving me away from the game. If I want to remain relevant I better do my daily chores or risk falling behind on the titanforge train. It’s awful.
This post is about BFA and BFA issues while utilizing a static and older design as a comparison tool. You are objectively wrong about the point of this post as it aims to get feedback on how to improve the dreadful state of BFA class design.
Lets not put words in anyones mouth here shall we. I can criticize classic. I can argue this topic belongs in classic forum. I can argue that most classic design elements have no place in retail. Do not, however, assume im not looking forward to classic. There is plenty of nostalgia there, of course. But classic got very little right in the long run.
BFA and it’s type of class balancing have sapped the flavor out of the majority of the classes from my experience. I have 6 120s and countless 100+. It’s odd when I play my DH and WW and feel like I’m playing the exact same class/spec.
So to trade it for another dreadful design - uhm no.