Yes, the routing is done by the sender, so he can decide to exclude
certain nodes, or nodes with more than nmax open channels. But this
requires some programming and struggling with the command line
interfaces of the lightning clients, I have not done that so far.

I do something similar when opening channels. I do not use the
'autopilot' feature of lnd but wrote my own algorithm to select
destination nodes: choose the nodes so that the number of hubs
required to enable me to send a certain amount of btc to every node in
the network is minimized, excluding routing through hubs with more
than 30 open channels.

By doing this one would set up a network that is more
decentralized. But I cannot claim that my node is excessivly used. (I
think the acceptance of lightning is still very poor).

If you want to have a look at my node and have any comments, its called
'node1'.