The problem with [primaris] dreadnoughts
Since I've been seein it around a lot, I will note that whats arguably the actual problem with the old firstborn dreadnought being 'squated' in favour of the shiny new primaris dreadnought model is that the new primaris dreadnought looks to much like the old one but messes enough with the design to make it unpleasant/unpalatable to look at.
namely the legs having an extra joint, its most obvious on the ballistus dready but that extra joint [at the knee] throws the whole design off balance by giving it legs that are ironically too long for its bodies design and shape to not be uncanny. the castaferrum is a squat lil dwarfy boy for dreadnoughts, but the primaris dreadies have the contemptor legs essentially which are designed for tall narrower/rounded bois with more human proportions. so you get the uncanny valley of a dwarf with long human legs.
and i can already point ya to a pair of legs that would have worked better for the primaris dreadies, and thats the leviathan.
the leviathan is not a dwarf dreadnought its a big honker, but it shares a general silhouette with the castraferrum in the sense of being wide and boxy, with what is essentially a squat posture. and its legs are designed to lean into that visual aesthetic being effectively more compact so more of the designs outline rests on the upper portion giving it a more solid appearance of weight. compare that to the contemptor
who has legs that are not only obviously thinner but obviously much taller in proportion to its body. and finally compare that to the primaris redemptor
whos legs are thin and tall [and even look more like the contemptors legs then the leviathans legs]. and to drive the point in compare to the ballistus as well which better highlights the problem
and for the sake of comparison heres a mortis castraferrum to further contrast things