If I had the answers, presumably MLS would be paying me A LOT of money.
I agree with @67YAZ about a Spanish-language strategy. Even with mediocre outreach and media at best, ratings for MLS and USMNT games are often better on Spanish-language broadcasts than English-language broadcasts. There's still a lot of untapped potential there.
I also think it might help if MLS teams could finally win the god damn CONCACAF Champions League. I'm not sure if Anglo EPL fans really care about that one way or the other, but consistently beating Liga MX competition would give the league some street cred among the largest Hispanic sub-group.
On the whole, I think it's good to have big names, but not too many famous post-prime players. Big names attract casuals who can be converted into regular fans, but if you go down that road too many times, you wind up as a reputation as a "retirement league" (grr) and that's a signal for Euro-philes to not take MLS seriously even if these "retirees" make up about 1% of the MLS player pool.
I believe that MLS becoming more of a talent-producing and talent-exporting league will help. The majority of soccer fans don't pay close attention to what's going on with FC Dallas or Philly Union or NYRB in terms of their academy pipeline. However, a critical mass of quality Americans (esp. MLS exports) in big Euro platforms eventually will move the needle of the opinion of high-engagement fans, who then act as "opinion leaders" or whatever for more casual fans.
I think MLS is better than it was in 2017, but certainly not dramatically so. But anecdotally, I'm seeing new interest in domestic soccer because of what's happening with American players in Europe. More and more people are recognizing that the men's side of US soccer is leveling up.
MLS recently adopted the marketing slogan "Our Soccer", which I really like. I think MLS should lean into being an American league that exudes self-confidence and pride at what has been achieved over the last 25 years. I want to see a bit more swagger and a bit more of a chip on their shoulder. Own and embrace the chaos and quirkiness of MLS instead of insecurely running away from it and apologizing for it. I think the quality of play and quality of development has reached a level where you can do that without looking totally silly.
To achieve the national relevance and TV ratings that MLS wants, there needs to be a critical mass of fans. I don't actually know very many MLS fans in real life, probably because I live in Boston where the Revs are barely a presence. A big part of sports fandom is engaging with others and right now we're in the midst of the long, slow slog of increasing the fanbase to the point where casual chatter about the league are ordinary, expected, and widely accessible.
