Not quite. Neanderthals were less social than us. They had bigger heads and bigger brains, so arguably, they could have been more intelligent than us. The problem for Neanderthals was that they could only trust and bond with a dozen or so others, whereas humans could thrive in societies as large as hundreds. There's some speculation as to why this is the case, but one reason may be that we were able to gossip about one another and remember more individuals, thus our trust network was bigger, and thus we could coordinate large scale hunts / attacks, and this is potentially why we could have overwhelmed Neanderthals despite their bigger size and bigger brains. I got a lot of this from the book Sapiens, as well as others, so I don't know exactly how 'up-to-date' this information is.

I think it's a bit of circular reasoning - Sapiens survived contact, Homo's niche is being the intelligent adaptive species, thus Neanderthalensis must have been less intelligent and/or adaptive.

Personally, based on the people I know with unusually many neanderthal alleles, I would guess the advantage had more to do with the size of tribes than the intelligence of individuals.

One thing that points to a big difference is art. There's some claimed Neanderthal cave art, but we're talking about things like pigment circles and lines -- nothing on the level of the modern human paintings at Chauvet or Lascaux.

There's enough evidence to convince me that Neanderthals decorated things and probably could think symbolically, but I to me, based on the evidence we have at least, it's pretty clear that modern humans went about this stuff differently.

I don't know if I think this really means "less intelligent," but I think this does point to some fundamental differences in how they thought. And who knows, maybe we'll find some beautiful Neanderthal cave art that disproves this. Our ideas about Neanderthals have changed a lot over the last few years after all.

We cannot be certain, but we know that their stone tools (Mousterian) are very, very conservative. It changed only very slowly over 250 000 years = a hundred times as much time as separates us from Classical Greece.

https://en.wikipedia.org/wiki/Mousterian