Unpopular opinion but I think it's acceptable as long as its optional especially as multiplayer game where they are hosting servers. Those aren't cheap and I don't have the game so I wouldn't know but if they do release more multiplayer content for free, I think it's further justification because that's better than paid content packs. As an example, CoD on PC had a recurring issue of DLC content being useless since too little people would buy them. Titanfall saw this issue as well and it was even worse due to the smaller player base. So with Titanfall 2 they just made it free and added cosmetics microtransactions that were actually reasonably priced.

Maybe this is not the solution for everything but as long as it has no bearing on gameplay what's the harm? If you're not one to spend on microtransactions then you only get the benefits. I don't think a more benign implementation should be criticised just because we fear the potential of it potentially becoming worse.