Either of the above would be a great help to players searching for a fellowship.
I agree the game is severely lacking in tools both for players trying to find a FS and for FS's trying to recruit players and I'd love to see some in-game tools added that address that deficiency. Many players have been asking for such tools for years.
That said, I'm not sure how useful a filter would be. I'm guessing you're on mobile and can't see a list of FS's like we can on browser, so you can't see how huge this issue is. I checked Elcysandir and there are 4816 FS's listed there. There are thousands that have 5 or less members.
Some are 'solo' players who don't want to play in a group, but want access to Tournaments and Fellowship Adventures so they form an FS of just themselves.
Many are players who quit the game years ago. If they had checked a box for 'Active Recruiting' at the time they quit, that box would probably still be checked and they'd show up in the search results. Even if the existing 'dead' FS were eliminated from future searches because they don't check the 'Active Recruiting' box, there are many players who start playing and form a FS and quit the game soon after that. The results returned would soon be too cluttered with these to be very useful.
Since it appears we'll be waiting awhile for the game to add more useful recruiting tools, there are some other places you can look for a FS:
The very bottom of these forums is a section by world with a place for players with cities in that world to post if they're looking for an FS and a place for FS's in that world to post if they're looking for players.
Platinum Leaf is a public Facebook group for Elvenar players and they have a
Fellowships Seeking Members section.
There is a player-maintained site:
ElvenStats where you can look up any FS to gather some info about it before joining. You can tell if it's active (players listed will have a black triangle next to their name if they appear to no longer be active in the game) as well as gives you info on the boosted goods of the current members and an idea of which boosted goods would be a good fit for them.
My personal recommendation: Try to find a group with players in a variety of chapters. While it's tempting to stick with a group of folks who are close to your level in the game, it's really hard to help each other when you're all facing the same challenges.