I don't think that "Peer-to-Peer" in the whitepaper's title ("Bitcoin: A Peer-to-Peer Electronic Cash System") refers to the network structure being p2p - and that's probably also not what most people mean when they talk about bitcoin being peer-to-peer. The very first sentence makes it pretty clear that peer-to-peer means person-to-person without any intermediary:
"A purely peer-to-peer version of electronic cash would allow online payments to be sent directly from one party to another without going through a financial institution." [1]
Furthermore, the previous title was "Electronic Cash Without a Trusted Third Party" [2]. So reading "Peer-to-Peer" as "Person-to-Person" would mean that the title hasn't changed in meaning, it just became a bit more catchy.
Also, when analysing the incentives of participants in the bitcoin network, it turns out that network nodes do not actually form the ideal-typical p2p mesh network (where all nodes are equally distributed and connect to a few other nodes) but a more densely connected network where connectivity to mining nodes is strongly incentivised. This topic has been researched and discussed by Dr. Wright (See [3] for more information).
[1] https://bitco.in/bitcoin.pdf
[2] https://nakamotostudies.org/literature/ecash/
[3] https://nchain.com/en/blog/bitcoin-network-topology-small-wo...