Last time I was making one (for myself, not to publish), my main issue was that browsers made it nearly unusable to have a private local extension because you only had two choices:

- either upload it on their website and go through approval everytime

- either lower security to run in developer mode, and have an alert warning you about it every X minutes, ruining your focus

VSCode on the other hand has no issue running local extensions at the same time as extensions from the marketplace.