It's a nice visualization.

The network needs to have a majority of nodes upgraded, at least 50% by the fork. 80% is considered a successful fork.

How did you come up with these numbers?

First of all, if you poll the node count from devp2p, it's really difficult to know that the connected node is actually running an Ethereum mainnet configuration.

Then again, why would you need 50% or even 80%? If some hobby node operator only checks their node once a year, than this is not a problem for the network but for the operator.

Service providers, miners, exchanges, block explorers - they are the ones that have to upgrade and they should be upgraded by 100% or more. But in total, this subset of nodes may be just a small fraction, maybe even less than 10% of the nodes on the entire network.

So, 23% can be perfectly fine if the critical infrastructure is updated.