Hi! I came across this korean guide on how to reduce Starcraft Remastered lag, especially on how to remove room lag, room list lag, room search lag, and channel lag, and some other methods for reducing overall game lag.

https://tobaek.com/300

English translated version using Google Translate:
https://tobaek-com.translate.goog/300?_x_tr_sl=ko&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp

Edit 1:
It seems that at the bottom of the page there are a couple more useful links for dealing with lag.