It’s not because how the game is balanced. But there are more mechanics and it has more depth in its core, so potentialy it can be harder to master.
Look at some newer weapons like 2h force sword - slide attacks, sprint attack. And there are old techs like push, push attacks, chains, special actions, different attack angles, perfect block.
What do you have with guns in DT? Buttstock special attack, torch? Yeah, there are 1,5 guns with special ammo. But as i said many times, there are no recoil patterns to learn. There are no extremely fast enemeis that perform teleportation, twitchy moves or dodges or have a tight weakspot hitbox.
When you switch your main melee weapon, you go and check chains. Or when new melee weapon drops. You want to know efficient combos for solo targets and hordes, wich attacks you can skip, block cancel, etc. With guns you don’t relearn that much.
You can watch new players gameplay, noone struggles to understand how to use plasma, reccon, flamer or rumbler. Meanwhile melee combat and melee movement takes some time for it to "click”.
It’s just in DT, unlike in V2, your offensive melee capabilities are much powerfull. So you don’t need to utilize block and shove that much in precise timings mixing it with attacks. And some deffensive layers are also much more forgiving than in V2 - toughness, dodge distance. So melee in DT is more spammy and arcade-ish.
But fundamentaly there are more inbuilt techs and just input buttons combinations for melee you can use.
And it always will be like that, cause melee has 2 layers - offensive and defensive and it breeds insane ammount of variables. You can look at PvP gneres. You can jump on any modern shooter or oldschool arena shooter and be somewhat average player. And you will find that a lot of things you learn are not about guns, but map control and movement. And those things you need to train muscle memmory for - they are not presented in DT gunplay.
But goodluck to jump in Tekken or MK even. Fightings are much more hardcore and so they are more niche than your average COD.
Like i don’t hate shooting, one of my all time favorite game is Unreal Tournament 2004. And in DT i played vet more than zealot. It’s just gunplay in DT isn’t that advanced or interesting to justify making it even more presented, imo.