While I also agree that Resilio could offer more active support for this product, for me it works as advertised, and with very few problems.
I hope if they decide not to do any more updates, they will at least open source it. If not, I expect them to release about an update every 6 - 12 months as they have been. They have taken steps like local sync, supporting Apple's M1 Chip, etc., so there are changes happening slowly. The product already does most of what you would expect it to, so I would expect new releases to be mainly bugfixes anyway.
SyncThing is still not nearly as good in some basic features, especially SelectiveSync. The workaround often given "Oh, just use .ignore files" is not realistic to the average user who wants to have a folder on their desktop that has dozens or hundreds of GB of data, and just sync a small portion to their laptop or mobile on demand for a short period of time.
With ResilioSync, you can have a huge folder and easily just sync the parts you need to work on today to your laptop by clicking on the placeholder files. When you are done working and the changes have synced, you can delete them from your local copy with a right-click "remove from this device". I use this workflow for davichi (video editing) projects all the time, and it works fantastically. If I want the files back after I have already deleted my local copy, I just double click them again, and they will be back with amazing speed since they are synched from my NAS and 2 other computers I use as RS servers.
Sure, I could edit the .ignore files and then delete the files manually (hope I get the order right, and no typos!), but at that point I could also just use use rsync or scp.
Another real-world use case: You have a folder with 300 DVD Rips. You have this selective synched to your partners laptop. When she wants to watch a video, she double-clicks, and it downloads and opens after about a minute. There isn't enough room to sync the entire DVD library, nor any reason to want to. You also don't want to ask your partner to fiddle with .ignore files just to watch a movie. You could use a webserver or something like Plex, but whether that is the style you wan to go with is another issue. If you want to have a local copy so you can download some movies before getting on the plane, then RS is a much faster way to do it than downloading via web, etc.
At any rate, there is no need to take my word for it - This feature is heavily desired enough that almost all commercial competitors have it already. Every year or so I check back, figuring "Surely Syncthing must have added it by now" - but they haven't - and to me, that means they are not even a serious contender.
I will admit, for server to server syncing of entire folders, the situation is different, and SyncThing makes a lot more sense.