Nobody is saying the game is perfection, in writing or in gameplay.
Nobody is saying it, but whenever legitimate criticism of the game's writing or gameplay arises there's always the inevitable comparison as to how FO3's and FO4's are worse, which terminates any kind of discussion regarding New Vegas' flaws. That, or childish strawmen like
@SquidVan 's.
However, given Obsidian have arguably not made a better game than NV since NV came out, means that we should not always take their word as gospel, as some of the changes to the design of NV that they wanted they got to implement in future games, arguably with worse results (see TOW as an example)
I can't speak about TOW since I never played it (the announcement trailer was enough for me to dismiss it, and judging from the fan response I didn't miss much). But New Vegas didn't need a massive combat redesign, or dialogue redesign, or quest redesign, and so forth. It just needed some basic tweaks, which mods were able to implement (to some degree).
The fact that they agreed to the 18 months is not exactly the greatest counter. We don't know what the conditions were exactly, but I can imagine that the temptation to do Fallout again was too much for the devs who had invested so much into that universe, not to mention the ability to capitalise on a newly successful franchise thanks to Fallout 3. Obsidian also had a track record in doing games in too little time and them suffering (KOTOR 2 being an example even if the final game is great.)
What happened is exactly what you describe: Obsidian knew they had 18 months, but aimed for the moon: this was Fallout, and they weren't settling for "small but complete and polished". Which is fine, but many of the game's issues arose because of that.
I think that either way New Vegas wasn't going to be as well received as Fallout 3 was: it received less than stellar reviews partially because it was based in Fallout 3, partially because of the bugs. Getting rid of the bugs (most of them, at least) but delivering a smaller game would have also caused reviewers to say "it's a small Fallout 3, therefore bad". And in that way, the game was rigged from the start: you just can't make a game as big or bigger than Fallout 3, with better looking assets,
and without bugs. In a way, Bethesda basically guaranteed New Vegas would never eclipse Fallout 3 when it came to critical acclaim. But because bugs can be squashed and writing is the one thing that can be much better without relying on a bigger game or better assets, that's where New Vegas shines brightest in comparison to Fallout 3.
Finally, we brought up the Beth games cause the creator of this thread did.
BiggumsBoi explained why someone may or may not like New Vegas, and he only got personal attacks and flimsy arguments as a response. He didn't even say the game was bad, just stuff that I also personally consider to be truth: that the game's story isn't particularly good (considering there's barely a semblance of a story in New Vegas; the minute you join a faction it's just "ok do all these things for me"), and that many of the quests are boring, and that as such that can be a turn-off for some people.
As well as know, "boring" is subjective. The idea that if you think New Vegas is boring then it stands true that you will find Fallout 3 to be even more boring is just mistaken, so I don't see why people use it as an argument that he was absolutely wrong. Some people think New Vegas is boring and Fallout 3 is very fun, others think otherwise.
A more productive discussion is "why do you find X boring?".