The problem is that we want to do both. The competitors to RTSes, games like League of Legends, Fortnite, Rocket League, and Hearthstone, are all (very different) games that are enjoyable to play across the full spectrum of skill levels.
RTS games really seem to be split into two categories: indie games that are appealing to casual players and competitive games that appeal only to esports competitors. StarCraft Brood War may be the most popular RTS from a spectator standpoint but it is a pretty terrible game to play if you just want to unwind after work.
So then the question is: why do we want both? The theory is that a highly popular spectator esport drives sales for the game. If your game doesn't do both then it either needs to succeed on its own (without any esports fame) in an overcrowded market or it's a spectator sport without any low-level players (and somehow needs to make money only from high level tournament play).