Multiplayer in Magic isn’t just free-for-all politics-heavy stuff like Commander - we just had a full set back in April based entirely around the Two-Headed Giant 2v2 format. 2HG is perfectly viable as a competitive format, particularly when done as draft or sealed.
The big issue with multiplayer in digital CCGs isn’t infrastructure, but screen real estate. Magic Online struggles quite a bit with this, but it at least makes an effort to offer it.