Ali
Frank
As racer three sixty pointed out in his guide the search foremost filters for highest number of cars in the tier as long as there's a free spot. The remaining manual filters seems to be only applied if there are enough leagues with an equal number. But if the leagues you actually looking for have just one car less then the game rather shows that other league even though its race is 12 hours off and the wrong number of cars per team.
I don't think this is the case Frank, given that I always used to have recruits even if numbers went down to 10 or 11 players in my 2 car league. When we had only 1 place free at Rookie level we never got any new recruits and as I booted people out for inactivity the numbers never increased. Something recently has gone wrong.
The suggestion list for new players indeed seems to have a different rule set than the normal league search. In the past it looked like as if it builds a pool out of leagues with room in the Rookie tier and rotates them, with almost full or completely empty tiers having some kind of penalty which makes them almost never shown and below about half full the chance decreased quite a bit as well, but I don't know if it really works that way, it just behaved like it does.
What I do know however is at least a big part of what recently changed. It's the more aggressive deleting of inactive teams. Due to that there's now way more leagues with open slots than the system is able to handle properly and thus it's quite a lottery to be advertised to the new players.