When people complain about something like balance, theyre almost always taking about the lategame, where the game genuinely plays pretty well and balance problems are relatively minor, and would be way pricier to fix. The *new player* experience is a much bigger problem:
Not only its genuinely the most 'unfun' part of the game, its by far the biggest impediment to SK's popularity and profits. Most people quit extremely early even if they would actually like the game, because the journey from 0* -> 4* gear is terrible compared to 5* gameplay:
-It starts out very slow and underwhelming: Charge attacks take extremely long, specially considering early game charge attacks are mostly just basic swings, and there are practically no sources of CTR in sight. You have little to no bonuses, and fight very slow and anemic enemies.
-Theres practically zero sources of interesting bonuses or progression to improve the gamefeel. Nearly all popular armor lines for newbies will have no perceptible difference between their 2* and 4* versions, or perhaps no bonuses at all, which makes it really unexciting. Theres not really any meaningful trinkets either, specially not one that makes a newbie consider spending 150e for slots. Early sprite skills are often nearly worthless without their ultimate upgrades. Almost all the early options with interesting buffs (ie: swiftstrike buckler) cant even be carried over into a *5 version. Sprite perks below 50 are no good either.
Im pretty sure most this could be easily improved with simple number changes. Make some early game weapons (ie: proto gear) charge faster, give players more sources of early buffs, make people see armor and shields as something other than something they need to pass Hall of Heroes... Some emphasis on giving a little bit of ASI and CTR as they are actually tangible gamefeel upgrades, unlike damage buffs.
And not only this would be much easier and cheaper to fix than lategame balance (for a much bigger increase in enjoyment), it would certainly be very meaningful for the profits, as it would make less new players drop it so early, so theres more players sticking around long enough to consider spending money. So please everyone, instead of screaming so much abouit brandishes, mixmasters, black kats and neutralizers... Lets have some emphasis on the early game instead, because its not only a much more realistic goal, it would probably put the game at a much better baseline for improving the balance of 5* gameplay.
In a market as competitive and arguably oversaturated in terms of multiplayer games, the first hours of a game are the most important to be able to earn players, and the amount of friction Spiral Knights has there in both gamefeel and progression at the beginning of the game is massive.
While there isn't a lot of problems when going through Tier 1 missions in terms of progression, missions feel like a slog because enemies are extremely simple and their damage is so low dying is kinda impossible for those remotely competent at the game, and your offensive options are usually kinda boring overall, with little build variety overall, as you said yourself.
Tier 2 and 3 start to become interesting and challenging in terms of fighting mechanics and weaponry, but progression is now the extremely boring and slow part, with very little options to earn a meaningful amount of crowns outside of Jelly King and the occasional Arcade run, and while you get a handful of orbs of alchemy by completing missions, the game tends to be very stingy with them in both mission competition rewards and loot found among levels, specially so during the 3* to 4* phase.
The cobalt set and weapons you get for free as you progress through ranked missions are also very underwhelming and kinda trick players into making bad loadouts and having a bad time overall.
Honestly getting friends into the game is extremely hard when their first impression consists of multiple levels where you just swing your sword or shoot your gun mindlessly against enemies that barely fight back or do anything interesting during fights, and "it gets good later" doesn't work when they can pick any other game that's on their library or free to play and start to have a blast there instead.