While I agree that the maps themselves are less memorable, that's more of an aesthetic thing, and I assume a limitation of their level design tools. I like the core art-style, but the maps look too samey/ lacking in visual character, and some of the free maps, even if they played amazing, looked kind of low-rent, as though they were built in forge.
As for multiplayer itself, it's easily a contender for best in the series in my opinion. I love the verticality that climbing adds, I've always wanted Halo to evolve into having running and aim-down-sights, so I very much like that addition, especially since it has such a perfect balance between ADS and hipfire, and plays like nothing else on the market. The guns feel amazing, and it has the best weapon selection in the entire series, nevermind a suite of excellent and ambitious game modes, bolstered by 2+ years of amazing post-launch content including the best Forge in the series, and finally...finally a server browser so we can play people's creations and mods without knowing them personally. Plus the game looks absolutely gorgeous on X1X.