For what it's worth, I bought a lifetime subscription for Roon, but still use Sooloos as my primary system. (I don't use Tidal either.)
(My Roon server has Control:PC installed with native export sent to the Roon watched folder - all media added to Sooloos pops up on Roon, occasionally used as a headphone zone.)
Original reason - checked before release that multi-channel cards could be used as multi-zone (i.e. like the Ensemble) - that didn't seem to make it to release, so I stuck with Sooloos and I eventually accumulated enough Sooloos zones that it wasn't important enough to look into again (or find where I'd put the cards I'd bought).
Sooloos is more streamlined and I can get straight to the music I want quicker (e.g. onscreen keyboard doesn't change position / keys while typing) not to mention that I can split systems and have a separate system with just my favourites installed (tag favorites, selective backup and restore to standalone remote system - no internet connection required).
Only slight annoyance with Sooloos - importing - would be nice to have an option to allow import when remote servers unavailable to allow import when you are nowhere near the internet, or the occasional outage (and as reassurance against future 'end-of-service') Also useful for bulk import of audio when you already know it's not in the database.
Shame with the price drop on the MC200, they didn't make the drop slightly less and switch to SSD at the same time (if people can hear the difference between interconnects on an MHR encrypted link, surely the spinning disk must be several supernovas worth of night and day difference...).
Legacy / antiquated is also known as 'tried and tested'.
Matt.