MLS is largely a pyramid scheme. Existing owners are mostly making more money from expansion fees than gate or TV revenue. Only a couple of the MLS franchises are profitable -- Seattle, Atlanta, and maybe a couple of the new teams that are still drawing well. The franchises also have to pay money TO the league in order to fund operations.
The league has enough momentum and rich owners to carry on, but if they really wanted to be successful in the long term, I agree they should be more innovate (at least from an American sports perspective). Unfortunately, nobody is going to pay a $100 million franchise fee that comes with the risk of being relegated to the NWSL, but one can dream...
As for stadiums, again, this is America, part of owning a pro sports team is that you have to get the local taxpayers to build you a stadium. You don't want to be a tenant at some other billionaire's publicly-funded stadium.