I don't have a solution for the competitive stuff (but I honestly think you are overselling it, AoE did just fine and you don't need this to be some kind of hardcore esport to keep a MP playerbase, just give us good custom map tools and people will play ElementTD until they croak), but they can just toss out the WoW lore. Say it's in a different timeline, or WoW's in a different timeline, or whatever. There's no reason they need to twist themselves in knots trying to incorporate the WoW lore, especially if they take the stance that not all returning Warcraft players will have spent any significant time in WoW (myself included) so why waste the time trying to explain nearly twenty years of WoW story developments when you can just say "that shit isn't canon" or "this shit isn't canon" or "who the fuck cares what's canon and what isn't, we just want to make the best video game possible."
I don't have a bead on the competitive scene, but I feel like RTS in general has too much of a skill gap for its own good. In my opinion the cognitive load you have to bear in competitive games at all levels is unwelcoming to new players and imo not fun. A lot of the individual skill gap need to be trimmed and instead the genre have to evolve to emphasize team games. All the popular online games, with the exception of a few genres (racing, fighting), are team based.
I've brainstorms a list of mechanics for the mp for Warcraft IV that addresses my issues with RTS, and if executed correctly would revolutionize the RTS genre.
- Instead of three-four factions, in multiplayer you pick a hero like in Halo Wars 1+2 that has their own unit composition. Some heroes are support heroes, others are carry heroes. This would balance the game towards team games. Additional heroes can be purchased as DLC.
- Main source of gold are not mines, but respawning creeps, enemy heroes, enemy units, bounties, etc. This encourages players to engage in constant action around the map. The stronger creeps / hero creeps on the map would need two or more teams to farm. I would also fix creep pulling so that creeping is fighting creeps not kiting creeps.
- Victory condition is the destruction of the main stronghold building in 1v1. In team games, it's a shared neutral building, similar to the throne in mobas. This would allow comebacks to be possible if one or multiple teammates were ganged up on and demolished. Teams should win together or lose together.
- The hero building that allows buy back of your hero can also teleports your units, perhaps only biological units, directly to your hero. This should greatly improve one of the biggest issues that plague every RTS game, pathfinding, as most of your units should be rallied to your hero anyways.
- No more artificial APM sinks like farms, and burrows. Supply is tied directly to your stronghold / keep level.
- To improve accessibility and adoption by new players, all hero, unit, and structure abilities can be set to be auto-casted intelligently by the AI. Obviously higher level players will disable this option, but this should greatly improve the barrier of entry by new players into the genre. They would only need to focus on troop positioning, and strategy. Warcraft's macro is already very simple.
- End game unit will a mechanic to end a stalemate, sort of like the Aegis of Immortality in Dota. The idea is that a boss creep can drop an item (Azerite?) that allows you to construct a super unit that if used correctly can tip the scales greatly. Killing the boss creep would require a major commitment allied forces, so it's a risky move that can lose the game, as the boss would be in a chokehold where the enemy can easily trap you in. Additional end game units type can be purchased DLC. You can pick a different end game unit the same would you can pick unit skins outside of the game. Balance should not be an issue because the unit is supposed to be unbalanced.
Example of end game units:
Alliance Skyship.
Draenei Dimensional Fortress.
Alliance Mobile Fortress on wheels.
Horde Red Dragon.
Horde Mounted Beast.
Horde Juggernaught. (Steam powered battlewagon)
Horde Black Dragon.
Undead Ariborne Citadel. (Final upgrade to the Undead HQ)
Undead Slaugher House on Wheels.
Undead Frost Wyrm.
etc.