The launch of 3.0 was fairly tepid as well. I kept going back to the hobby shop for months, waiting for a new book to come out, and usually there was nothing. I picked up a few of the early 3rd party books and the quality was...unique, I'll say.
Then once supplements did start coming out, well...Sword and Fist and it's cousins were pretty wonky, and I'm pretty sure WotC knew it.
The 3.5 versions were better produced, and the content was a little less...shaky, but anyone who has ever read Complete Warrior can tell you that it was a mixed bag. Many options were fairly conservative, but years later people were still finding ways to abuse Warshaper.
As an aside, that was always the problem with 3e- the sense of scale was always off. Every book had a combination of good, bad, and just plain weird, like WotC staffers were just throwing darts at a wall to see what stuck.
Even rebalanced options, like variant character classes never said they were such, and I imagine many a DM was confused about whether or not having a Dragon Shaman and an Archivist in the same party was a good idea (pro tip: no, it's not).
Personally, when the topic of 5e's quality comes to mind, I'm not really finding the quality lacking- the game gets new players into it and ready to play fairly quickly, which is very important. My problems more have to do with long-term play, how it performs over time as you reach higher levels, and consistency, because, just like every other D&D product WotC has ever made, even within a given book, you can have great things, decent things, terrible things, and questionable things, which really begs the question of what metrics they use when creating content.