Yes, but no.

First, if they deleted thralls, that would get rid of many of the issues people have because it would get rid of many of the people. The things that makes this game stand out, especially as the fantasy adjacent survival genre gets more crowded, are what keep players around. Once all the players are gone, their complaints will go with them.

Second, removing thralls would make some of the issues worse. Thralls tend to be at least vaguely competent with Two-handed Swords, One-handed Maces, and if placed correctly, Spears. Katana seems to be getting a bit better?
So, if a player doesn’t like the moveset for one of the weapons a thrall can use with vague proficiency, then at least that weapon can have a use.
Don’t like Greatsword attack pattern? That’s ok, throw it on your minion. No minion, no use for that blade of the betrayer.

However, you are correct that a strong slice of the issues with Legendaries also exist independent of thralls.

This is a dovetail.
A moveset can be good if the risk is worth the reward.
That doesn’t make it fun.
People don’t only have preferences based on pure efficiency, they may actually want to enjoy the process of winning. This is a difficult thing to gauge, because we don’t all enjoy the same thing.
The single handed Mace moveset is good. But that doesn’t mean everyone will take pleasure in it.
The Shortsword moveset is extremely narrow in it’s utility, but this one enjoys it all out of proportion with it’s relevance.

Now, if someone cannot find a weapon type they enjoy in this game, they won’t keep playing. Unless the allure is the Masochism. If someone sticks with it, there is probably at least one attack pattern they find fun. Maybe more, but at least one.

The issue with simply buffing existing weapons is that, no matter how good the numbers are, if the actual using of the item gives no pleasure, if it is a chore and obnoxious, it’s not going to be a thing that makes someone happy to acquire.
If someone hates archery, no amount of armour penetration and damage will make that bow a joy to find.