I haven't replaced my lights for an extended period and am wondering if that's why they are dim, but if they burned out that fast they were probably getting some kind of contamination on the bulbs (which concentrates the heat).
https://www.theautodoc.net/blog/why-do-headlights-become-clo...
The other problem is that some bulbs are just not very good - the filaments aren't properly positioned, or they don't have a good spectral output.
3M has a kit for polishing the haze off headlights with a drill, and for restoring the UV protection layer [0]. Dan Stern [1] told me it's really better to just get a new OEM headlight.
[0] https://www.amazon.com/3M-39008-Headlight-Restoration-System...