> Maybe a shorter duration(<5yrs) patent(for lack of better word) for unapproved generics might do the trick.

There already is something similar - the NDA exclusivity period. You get 3-5 years where the FDA won't approve any other versions of the product.

https://www.tandfonline.com/doi/pdf/10.4155/ppa.14.30

But ambroxol isn't a decongestant - it supposed to help with phlegm.

Ambroxol is not a decongestant, it's an expectorant. If you take Ambroxol expecting to clear your sinus pressure like pseudoephedrine, you're going to be disappointed.

I've used it. I thought it was going to be better than guaifenesin (equivalent available in the US). In my experience, it was not.

That entire blog post appears to be based on a second-hand report from someone who went on vacation in France and was told something by the person at the pharmacist selling them Ambroxol. I don't understand why rationalist bloggers are so keen to rely on anecdotes and hearsay when it supports a point they're trying to make.