If you think AR's are boring, you aren't doing them right.
I have 12 different AR15s and variants, ranging from a 7.5" AR in .300 Blk to a belt-fed Fightlite MCR, with everything from an originial AR10 to an LWRCI M6IC, with Colt Canada and HK in between. All are fully accessorized with optics, lights, lasers and various other useful accessories. To say that I am thoroughhly bored with AR15s (and their piston variants) would be a vast understatement....
Now, when you start talking ACR, MCX, X95, Bren 2, B+T APC, FS200, Valmet, AUG, Galil ARM & SAR, G3, FAL, AR180, FNC, SIG 550, G36, M7, or any interesting NEW design, I start to get interested, The R18 Mk2 therefore intrigues me as a new, hybrid combination of several modern designs.
That's it, that's my main motivation WRT small arms collecting - the key past, current and future designs. I am not particularly interested in a single design such as the AR and its variants, regardless of its success. Just about everything that there is to develop or enhance with the AR15 design envelope has already been considered or done. As a result, ARs have become somewhat boring to me. Obviously YMMV.....