The monsters, the environment, the armor. All of that art looks markedly worse. That's not cherry picking. Is an opinion, sure, but I can be fairly sure in not liking the direction they're going with the visuals.
The art direction looks identical to me, but with higher quality assets. Been playing the series since PSP and I'm just not seeing this drastic difference you're describing. The armor shown is very reminiscent of early armor sets like Steel or Hunter. The Rathian looks identical to all previous incarnations albeit with higher polycount, texture count, normal mapping, etc. The environments look to be more detailed versions of typical monster hunter areas, albeit we are limited to one locale which appears to be a tropical island setting or sorts.
So yeah, just not seeing it.