Inter and Big RR were removed from Free league when they were added in Allround league (and in default/rope). No scheme is in both Allround and Free league. When you play Inter, for example, the game is counted in both default and allround. Rope and default ladders give people another incentive to participate in the allround league. I'm sure many haven't even read the announcement regarding rope & default ladders so they don't know how everything works. I agree it's a bit complex system but activity isn't being split between leagues.
Allround seasons were 3 months long. Activity had dropped close to zero and there was no hope of playoffs. Instead of starting a new season every 3 months, MI decided to make the season indefinitely long so that people could still report their games.
I still don't believe the allround league would become any more appealing to newcomers if we added Mole Shopper etc. You'd also need to remove most of the Classic league schemes.