Exactly. She was clearly being written as an alcoholic but the writers, wisely, realized that there was little humor to mine there, or at least mining it took more skill than they had.
It was pretty soon after the not remembering whether or not she had had sex with Raj (not a decision a sober Penny would have made) that they began to pull back. S5 the girls playing Twister Penny drinking while playing (no one else drinking) and passing out. No BBT expert here but the last bit I can recall was Leonard in S7 saying that it wasn’t a good idea to take Penny to Napa, to where the wine comes from, and then backs down some, just joking, but you might have a problem. Since then? The character’s drinking is way toned down.
The days are long past of an Otis drunk being “funny” and addressing a serious substance abuse problem can be dealt with with humor by a skilled writing team but they did better letting Penny become the more mature person in the crowd and backing away from that direction. IMHO.
Actually I wonder if that has been a shift … from the original Leonard as the viewer’s identified saner person in the midst of eccentrics, to Penny as that identified character more so …