Absolutely, that is indeed the situation right now - to rebuild and expand on Chris's incredible legacy of emulation work will take a lot of coding and reverse-engineering... but that said, steady progress is being made in MAME-based FME
As fruit machines are very niche compared to even pinball, we are short on coders with the requisite skillset+motivation - so patience is the name of the game right now. Hopefully in a couple of years or so, Arcade Sim (plus the new MAME internal layout/config work), will make developing/rev-engineering these drivers more appealing, so more coders may get involved - but we already are seeing great progress over the past year; James and David have pretty much done Impulse hardware, and David is massively pushing forward on MPU4 (most notably the new Chr chip work which has revealed previously unknown patterns wrt. lamp scrambling). And of course @SomeRandomGuy is absolutely killing it on the early techs right now
I plan to always keep MFME support in AS (when running under Windows OS) alongside MAME so the Pluto 5 games will be playable for MFME users before Pluto platforms are done in MAME. On a somewhat related note, the user @Sneddrs has had Arcade Sim working fine on a newer Apple Mac M1 under Parallels:
... so great news there , and it sounds like MFME-based fruities should also work fine under that setup . So while not a true native Mac version, it does sounds like it's already fully working 'for free' on the new Apple silicon macs.