Bad tasting avocados recently
"Watery, grassy and bland" and "not mushy/creamy" (a.k.a hard) match my experience of avocados that aren't sufficiently ripe. An avocado should be very soft and creamy when it's ripe. (But not brown/grey/gross - that's over-ripe.)

At least in Israel, avocados are sold somewhat unripe, since that prolongs their shelf life, and because soft ripe avocados bruise much easier than rock-hard unripe ones. If you buy an avocado that isn't ripe yet, you should wrap it in some newspaper, and leave it out of the fridge until it's ripe. depending on how unripe your avocado is, that can take a week or more.

I'm afraid I don't know the names of American Avocado varieties, but my experience has been exactly the same with the green smooth-skinned elongated ones, small black rough-skinned ones that peel easily, and roundish, leathery-skinned green ones. When ripe, they all taste pretty much the same.