There is a a whole cottage industry of people who make classes. On DMs Guild, or GM Binder or D&D Wiki. You want a warlord? There are several to choose from. Psionicist? I'd guess a half dozen takes on it. Witches? Several I have personally tried. Swordmages and summoners and shamans? Seen them all. There is a market for classes WotC won't make, but I've not seen a market for mythic, mountain -throwing martial classes. If there IS one, id love to see it. Please link it to me.
Because I see a lot of theory crafting and blame, dusted in a light sprinkle of edition wars, but I don't see a lot of solutions aside from some nebulous idea of bringing the 4e fighter back or nerfing wizards (or the occasional rewrite D&D from the ground up). It's like discussing politics; everyone is sure what the problem is, but nobody has a plan or fix it besides changing the status quo and removing the Other Party that's enabling it.
So I'd like to see someone's attempt to fix this problem. If the problem is as widespread as stated someone has to have cobbled together an attempt to fix it in the last nine years.