Gameplay wise there is nothing wrong with it. There can be social/financial issues with microtransactions generally for people vulnerable to spending, but that's quite a whole different topic.
People mostly complain because nowadays you'll also not get a finished game anymore at launch. We're already only buying licenses without any reselling value, and many games are in a decent state months to years after launch, which should have been actual development time. The 'games as a service' model is often being abused to actually ship an alpha version of the game and excuse bugs.
I wouldn't trust any game company on their promises, especially not if publishers are behind them that have proven to cut content and sell it later as DLC.
We'll see what Relic will do, but since these MTXs can heavily influence the game's design and balance, it's necessary to draw a red line before important design decision have been made
I completely agree with your post but want to explain why I'm more optimistic regarding Relic's dlc politic:
I'm convinced that they know that a "fair" dlc policy is needed if they want to establish the game as service game: In other words: They will make more profit if they treat the players better (no op commanders, good quality dlcs instead of bad designed copy and paste doctrines).
Regarding cut out content:
I know that a lot of companies have done that in the past and that's shit. But some players don't want to understand how production in the gaming industry works. Take a battlegroup for example: Before Relic can sell a new doctrine, artists have to draw, units need to be modeled and testing have to be done. If Relic does want to support the game and keep it fresh than they alrdy have to work on mp and sp stuff or we will have to wait a long time. And then players would complain why the game doesnt get the much needed content.