"Neanderthals appear to have matured faster physically but had a slower reproductive tempo overall, with longer spacing between births. That suggests fewer offspring over a female's reproductive lifetime."

So my theory is that they could well have been more sophisticated in a lot of ways, but were just outbred.

Seems like that would go right along with using fewer calories. Very interesting.

Ive also read some out of wack theories like some conditions like autism could come from them since its more prevalent on white people. This would explain that a group that engages more socially creating bonds and more complex societal tribes in number would outnumber and extinguish these weird less verbal humans

There are some relevant studies which suggest a connection for at least some autism spectrum folks:

https://www.nature.com/articles/s41380-024-02593-7

https://www.nature.com/articles/s41598-017-06440-4

It's far from conclusive, not representative of the majority of folks with autism diagnoses, and needs more replication and investigation. But it could be a thing. Speaking as a spectrum-y red-haired middle-european.