KEF ls50 metas were the biggest disappointment I've ever had - got sucked in by the reviews and trust the brand; I have a wonderful pair of (late 60's?) KEF Concord (I think but the fronts are different) a pair of Celeste mkIIs (still an adequate speaker) and a couple of pairs of Quad ESL57s as well as countless modern B & W (705s and others) and Mission stuff.
To be fair it may be the unusual placement (on a plinth in the middle of the room alongside said Concords) and they may be happier with the usual stands on the floor but I got them to replace my vintage beauties. I thought they would be crystal clear, image well and sound 'fast' at the expense of some warmth but they sound on the flat side of neutral- just dull