Agree, it makes sense to go to MLS teams just to make money or live somewhere else. I think it is no different than Arabian teams. You can go to these teams to earn money in the last years of your career, but it wouldn't make much sense to be here at a young age. Prevents you from progressing in your career 
Yes everyone will go to the Saudi Pro League or MLS League at some point but not right now. Pulisic and other players of his age still need validation to prove their quality and even become the best players before they land in a league that is not yet competitive. Serie A, EPL, La Liga, Bundesliga and Liague 1 are great places to prove yourself. Maybe at the end of a career it would not be wrong to choose a league that is under five, in this case the MLS or the Saudi Pro League to make money.I think Milan have a special relationship with Chelsea in buying and selling players, the two Chelsea players Pulisic and Ruben Loftus-Cheek who landed there prove that. This means that there will be at least four former Chelsea players who will play for Milan next season, and the presence of these two new players will be able to add to Milan's power on the Champions League stage.