Yes, the debts Satoshi owed to others were obvious right from the start. I made pretty much exactly the same argument as OP over 6 years ago in my then-widely-read essay "Bitcoin is Worse is Better" https://www.gwern.net/Bitcoin%20is%20Worse%20is%20Better - Bitcoin built on many established tools and concepts and its true contribution was putting them together in a way that was conceptually alien and disgusted people immediately on arrival. (Proof of Work still viscerally disgusts many people! _plus ça change, plus c'est la même chose_ eh? Anyone can invent something that everyone wants - everyone wants a cheaper or faster computer, for example - but it takes genius to invent something that everyone hates, thinks is useless, wasteful, evil, or all three simultaneously, and eventually wins grudging acknowledgement that it may actually be a good idea.)
It's nice that Arvind & Clark have gone into more detail about the predecessors, though, I suspect that most Bitcoiners these days have little idea about it (although I think they overstate a few of them - Satoshi didn't know about B-money until he was told by Back and so most accounts of Bitcoin's genesis overstate its influence).