Filtering the displayed ones on the client side would help framerates and such, but if the server can't keep up, that won't help. It needs to be a server side fix.
I agree with you entirely, it needs to be a priority. But it's been a problem since 2.0. Ixion still does it today on my server, although it's less severe than the Eureka train because there's fewer people there. It's not something that can be a quick fix given the code in question affects the entire game and any bug would be literally game breaking for affected clients.
I hope they make it a priority for 5.0, but I'd honestly be very surprised if anything happened before that except perhaps lowering the population cap.