devtrackers.gg
All other criticism aside, I feel this will be the single biggest issue that can heavily thwart the popularity of the game during and even post- 'Early Access'. 'Riding the wave', player-base wise, of this initial launch by having the Map Editor available right off the rip (and allowing custom maps/modes to be played) would be the single best way to retain a massive portion of the player-base for this game.
It is probably much too late for this to change now, though I can't stress enough the importance of 'sooner the better' for the Map Editor's release. 'Sometime in 2025' will feel like a millennia in today's games market if there isn't enough content otherwise, especially accessible freely, to keep players' attentions.