Long term, I think it would greatly benefit US soccer if they went forward with a relegation system similar to the rest of the world. It probably will never happen as MLS owners have put too much money into growing the league and they don’t want to risk losing money.
Having multiple tiers would allow for additional professional teams across the country. The potential to get to the top league would make it easier for the cities to get behind their teams and support them, consequently getting more people involved and caring about soccer etc.
Imagine if places like DSM, Omaha, Milwaukee, and on and on had professional teams that had a chance to make it to the MLS.