> We use Helm at work, and our charts are 95% hard-coded YAML templates, with an occasional sprinkling of a Helm variable for values which differ between dev/test/prod. It works great and is a ton easier than Kustomize for that purpose.

I have come to precisely the opposite conclusion. I can count all of the helm charts that didn't make me immediately want to cry with one hand... and I'd have at least 2 fingers still free.

If you have "base, and then we change three things per environment", Kustomize is about as good as it gets using simple patches.

at $dayJob, we have templates wrapping templates and not a ton of tests on anything. Lots of implicit defaults that are not documented anywhere other than in the master/root chart defaults. As far as I can tell, this was how policy was meant to be enforced rather than something like OPA.