I could still use an explanation of this mythical in-depth melee system the game had because literally as far as I am aware, the game had Lights and Heavies for attacks, weapons themselves had their own patterns of attacks which could be comboed, you had block and push which had their own version of follow up attacks, and then dodging. All of this exists in Darktide, so I would very, very, very, very much want to know what in the world is locked out of the melee system of the game until you play Cata for a living?
The reason why I am going on and on about this is simple. I personally have none of those issues you listed in your original post, mostly because I see this as a simple shift in what your available resources are. Instead of having several, individually regenerating stats that refresh while you use others, DT very much focuses on resource conservation as a whole. Your stamina drains from sprinting and blocking, but not dodging, however it doesn’t regen either. Dodging obviously has the dodge cap, so you have those to keep an eye on. So where is the conservation coming from? Grenades and/or Class Abilities.
The attack waves in DT for melees outside of Endless Hordes (Or High-Activity Area as it is now known as, bleh) aren’t nearly as large as they were in VT from my recent memory, again it has been a bit since, due to the addition of the ranged combat focus in the game, thus you are not assaulted by nearly as many runts as you were in VT. You are instead assaulted by more variants of Specials and some Elites, which probably cause the biggest issues in melee due to the Poxwalkers and other trash mobs being significantly slower to attack like you mentioned initially compared to Slaves and Clanrats.
Notice how currently in DT every class has a tool to clear a path out of a tight spot. Veteran has Greandes, Zealot has the Stun Grenades, Ogryn has the Bull Charge and Psyker has Psykinetic Wrath. This is something you have omitted entirely from your initial criticism towards the current melee system, which is exactly what tells me that while I might not know anything about VT melee system on “high level”, it shows you don’t know how DTs work because you very much try to only utilise your skills you ported over from VT without adaptation.
Personally, I like the way DT does melee because it is mechanically more strategic that reactionary that it was in VT. You didn’t really need to track your own resources in that, as everything regenned when you weren’t using that defensive measure, thus you approached the matter similar to a fighting game. You never need to exactly worry when you might reach, say, your block limit, because if you played your class enough, you knew that you can take only X number of hits, so you block just one prior at most, then switch to the next measure, such as pushing or dodging, so it becomes similar to a fighting game.
DT on the other hand gives you a limited pool of resources, meaning you need to have a plan from start of the encounter to the end. Plan your route of kiting, make sure you don’t start throwing 'nades without thinking just because you see a big mass of bodies coming your way, don’t instantly use your abilities if you aren’t confident enough about your chances. Again, this makes it less about only reacting like you would in VT, you know you need to end the fight as quickly as you can before you run out of your resources, thus making it more strategic than reactionary as your focus shifts from one to the other.
I hope this makes the argument I am trying to make a bit more constructive and less sarcastic, which I must apologise for, because I started very rapidly sounding like a salty 5 year old. So to summarise, Darktide takes a different approach to the melee system we had in Vermintide, basically the downsides you mentioned give the situation a very bad light because you are totally ignoring an entire addition to the combat mechanic, aka the existence of 'nades and certain abilities, as VT had random bombs here and there but let’s be perfectly honest, they were just that, random, so you couldn’t by default rely on them to be your trump card out of a situation.
I hardly see a difference in combats for that reason, as they approach a similar situation with different goals in mind. In VT, melee is more about outplaying your opponent and widdling down the horde while in DT it is more about outlasting the horde as you try to find yourself a narrow corridor to funnel the enemy through, or just try to take them out as quickly as you can before you do run out of resources. In other words, different strokes for different folks.
What I would like to see first before any major changes are done is simply refinement. First of all they need to fix the netcode before they start fiddling with mechanics because that is the biggest issue right now, Ragers being able to swing at you from double the length of their melee weapon is a bit daft. Tweaking and balancing of things, stuff like that. Personally, I would like to avoid to have VTs melee system ported over because it simply makes the combat, again, more about being hyper conservative and slowly chipping the enemy down with reactionary moves instead of having to plan the whole process and improvise on the fly when things go south.