Ooh, that is a hot take! I didn't read the Kobold Press book, so can't offer an opinion there.
Most of the worst offenders are just weaker and less versatile variants of existing spells.
as for classes, Kibbles’ does alright, but the vast majority that I’ve seen (and I’ve seen a lot bc even the bad ones have some gem ideas sometimes) are very poorly balanced, to the point of being dramatically outside the power curve of 5e. It’s a robust system, but there are limits to what will run well in the system.
Mostly I have been disappointed every time I’ve heard “this is better designed than the official stuff!” And then gone and read something that is fine. The ratio of good to bad is much better, IME, in the official material, and the problem stuff is easier to fix because it’s more likely to still be fully written in the style and format of other official 5e options.
I know how to fix the 4 Elements Monk, without a full redesign. I’ve explored a few more out there approaches (like giving them the Mystic’s Wu Jen elemental stance thingies), but all it actually needs is to be able to “nova” by throwing a burning hands and flurry of blows in the same turn, to know more disciplines, and to make the disciplines cost on the same scale as other Monk subclasses, ie 1 ki/spell level.
An extra way to regain some ki a few times a day wouldn’t hurt, but isn’t necessary.
To make it shine, only requires the above, and something like being able to make thier attacks deal extra elemental damage.