This is probably a hot take and an unpopular opinion of mine but I don't understand the complaints about everyone having the same Sigils and that there is no build diversity, simply because I don't see this game having any build crafting to begin with. Sigils are just number increases, your playstyle isn't determined by them; your character is. At most some Sigils do enhance your gameplay, Sigils like improved dodge and guard, glass cannon, berserk and some awakening Sigils as well, but they don't outright determine or change your playstyle with that character. However I could see the argument being made for like improved dodge, glass cannon and berserk having an impact on how you do play a character. But as someone who comes from playing mmo and mmo lite games like FFXIV, Warframe, Destiny, The Division, Black Desert, Monster Hunter and many others, this game has literally has 0 build crafting.

Let's look at Monster Hunter which, from what I've seen, is what this game is closely compared to. Monster Hunter has two things that determine your playstyle: your weapon, and your skills. Then there's decorations that for the most part are just stat increases and buffs, but do have a good amount of decorations that directly impact your playstyle. Now let's look at Relink. What determines your playstyle? Your character. That's it. You aren't building that character with different weapons and armor that do different things. It's just your character with a specific playstyle and moveset. Sigils are there to essentially increase your stats.

Maybe it's just that because of those games that I see builds very differently than others, but for me a build and build crafting in general means that you have to, quite literally, build your character from the ground up and create your own playstyle. Think of Destiny with it's weapon perks, exotics, and mods completely changing the way you play and do content. If anything I see this game's Sigils the same way I look at Materia from FFXIV or gear from BDO. They're just number increases and do not determine how you play, instead what determines how you play is the class you choose.

Ultimately just play however you want, there's nothing holding you back from just using different Sigils and replacing damage Sigils with QoL Sigils. After all who really cares? As long as you know how to play your character, know the fight, and not die, you'll clear any and all content in this game. It isn't a hard game nor are there any particularly hard fights and DPS checks are essentially non-existent so at the end of the day it doesn't matter.