This is just me, but the move I would be most interested in is if he started one band and dedicated a significant amount of time to that one band, focusing on quality musicianship and songwriting instead of on names and nostalgia.
This may sound harsh, but my perception of the projects he's been doing is that every year or so, he gets a new idea for a band. This band usually consists entirely of friends of his and/or semi-famous musicians from bands that were big in the 80s. The band is usually billed as "this sounds like [style of music that was big in the 70s or 80s]." If it's not just a cover band, the band writes an album in a really tight time frame (because Mike has eight other bands to schedule), and usually the haste is apparent in the songwriting. Then there's a tour crammed in between three other tours Mike has scheduled, where half the setlist is covers from bands that this new band was clearly intended to sound like, topped off with with Blu-Ray release. Then the band goes on the back burner while Mike cycles on to a different project.
I think that these projects do not last primarily because not much time and care is put into them. As many have pointed out, Mike has this thing about sitting down to write and record an album in two weeks or something. That might be something you can pull off if your primary songwriter is Neal Morse, or someone similarly prolific, but most of the time doing that seems to cause the songwriting quality to suffer (it probably suffers some even when Neal rushes it, compared to projects where he takes more time). If there wasn't this pressure to pump out an album in the shortest interval possible because of eight other projects waiting, maybe the songs would be better.
And another thing that might make the songs better is if the members of the band were selected specifically because of their musicianship and songwriting ability. Not to put down the musicianship of anyone in particular that Mike works with, but to me it seems very likely that these people are not being selected on that basis, but on the basis of "oh, this guy was in that one band." Maybe this is just because Mike likes working with guys who were in bands he likes, or maybe it's because he or someone thinks a project is more marketable when it has some big names, but to me it is very clear from the promotions (Mike's and the labels') that we are meant to care more about who the band members are than whether the songs are good.
The thing is, I sort of get the motivation behind that—there's an argument that it's easier to sell a known quantity than a newcomer—but I think it misunderstands how music works in 2020, particularly in genres that tend to draw more serious listeners, like prog. A name helps to get listeners to your music in the first place, but, in an age where anyone can sample anything on Spotify (where only pennies go to the artist), what gets them to actually buy albums and concert tickets is the quality of the music. Mike Portnoy is a big enough name in prog metal to where he doesn't need four other semi-famous guys to get people to try a new song. But what is going to get people to do anything more than just try an album on Spotify is the album being good. And not just the "well, it's decent" sort of good that seems to be the typical DTF review of the two SOA albums, but actually, convincingly, good. Good enough to stand out among the Hakens and the Leprouses and the Caligula's Horses.
It's not like Mike is incapable of playing on an album that good. I'd say the last two Neal Morse Band albums have been very, very good. But I think making that sort of album requires time and dedication to songwriting in the sense of driving at writing good songs, not driving at writing songs that remind people of 1987. And the way to get to good songwriting, especially when one is a drummer (and thus probably not writing a lot of riffs and melodies) is to select good songwriters in the sense of driving at selecting good songwriters, not driving at selecting songwriters who were famous in 1987. Honestly, look at Neal Morse (even those who don't like his music; this is just a good example of how to do things right). He brought in two guys (Eric Gillette and Bill Hubauer) who were pretty much complete unknowns, because he thought that they could elevate the songwriting and musicianship of his band. And it paid off in the form of his most highly acclaimed "solo" album in years (The Similitude of a Dream), which seems to have brought back listeners who thought his approach was getting stale and brought new listeners in. Because he brought in talented people, took the time, and the songs were good. Mike isn't as much of a songwriter as Neal, but there's no reason he couldn't do that for a metal project (which seems to be the niche he's struggling to fill). Drop a lot of the minor projects, keep NMB and FC (and TA as an occasional thing), and seriously look for who are the real talents in metal who have time to invest in a new project, without regard for how famous they are. Then dedicate some serious time to writing a good album and... people will come. They've come for a lot of other bands that didn't have the advantage of the Portnoy brand to help cut the line. Just so long as the music is good.
As others have said, maybe he's just happier doing what he's doing, putting out middling nostalgia albums with people he likes. And that's fine if he wants to keep doing that. But I think there's a clear blueprint for what to do if you want to succeed in today's metal/prog metal world and sustain people's interest and excitement, and the place that he's in right now where he starts a dozen projects, few of which enjoy much critical success or popularity and most of which flame out within a few years, is a place that he's more or less choosing to stay by pointedly not following that blueprint.