Bethesda have never been good at quest design and the only good writer they had, MK, left after Morrowind. blah blah nostalgia goggles blah
Nah my nostalgia goggles only seem to kick in for things 10+ years old. Oblivion had some very notable quests and so did Fallout 3. Very few Skyrim quests stand out by comparison, there was a greater focus on quantity over quality. The murder mystery at the lighthouse (which quickly turns generic) and the Thieves Guild stuff were the only ones I can even recall as memorable offhand. Just even doing a basic comparison between something like the Mage Guild questlines in the various games is pretty telling.
Writing quality is a different story but it's hard to determine whether this is just very weak writing or the writing is poor because the structure has to accommodate the poor variety of quest types. Maybe a little from both. I do agree that Obsidian with Bethesda's tech is RPG bliss, I loved New Vegas and you're right that FO3 had better exploration.