I wouldn't call Paxos on the decline. It has several nice properties that Raft lacks[1]. However, implementing it correctly is more brutal than Raft, which is cut into easier-to-understand components.
Also, the paper introducing Paxos[2] is famously obfuscated, while the Raft website[3] trivializes the problem, and has ready-to-use libraries.
As a result, there are more recently-developed systems in Raft than Paxos, but I expect there is more volume hitting Paxos systems than Raft ones in the world.
As a member of a team that has implemented Raft in production (https://fauna.com) and in conversation with others who have, the general consensus is that Raft, Paxos, and even Viewstamped Replication are variants of the same fundamental algorithm.
Thank you for sharing an interesting paper. The similarity between Raft and Viewstamped Replication is easy to gauge. The original Raft paper too acknowledges this similarity. OTOH, the similarity between Paxos and Raft is not very apparent (to me). The paper in the link seems to predate Raft, and only considers VR, Zab and multi-Paxos.
Also, the paper introducing Paxos[2] is famously obfuscated, while the Raft website[3] trivializes the problem, and has ready-to-use libraries.
As a result, there are more recently-developed systems in Raft than Paxos, but I expect there is more volume hitting Paxos systems than Raft ones in the world.
[1]: http://rystsov.info/2017/02/15/simple-consensus.html
[2]: https://lamport.azurewebsites.net/pubs/lamport-paxos.pdf
[3]: https://raft.github.io/