I can subscribe to a lot of the feelings expressed here, by the OP.
When Rick Priestley designed Warhammer Fantasy, he was basing his ideas of ancient/medieval combat in 70's and 80's historical wargames. Of course he took ideas from there, and attempted to create a similar feeling for fantasy armies battles. So, I'd say it's natural that anybody comparing FB, AoS and 40K will see and feel the difference.
But one thing I'd like to stress is that none of these games really wants to be a simulation. Rick & other game designers have been quite open about designing entertaining games with a lot of feeling, not simulations. Simulative regimental, skirmish and firepower games tend to have different kind of rules, and although the feeling can be the same, the decisions and tactics the gamer makes tend to be somewhat different.
-Z