I believe that the slowness is a matter of the amount nodes in the tor network, not something that can be fixed solely by code changes.
No one is claiming the new version is faster, only that it is safer.
completely agree but it could be added that a new language can sometimes help explore new ideas faster, in which case maybe the routing layer and protocol can see new optimizations
This is not correct. Tor is generally not bottlenecked by the quantity of available nodes, the usual bottleneck is the quality of nodes picked by your client rather than the quantity of nodes available.
Of course, technically, this problem is related to the quantity of high quality nodes :)
It’s important to remember that safety is the whole purpose of the thing. If Tor is slow, it’s annoying. If Tor is compromised, people get imprisoned or killed.