Chess.com servers are known for being slow and crashing often, people say that's why lichess is better but chess.com also has way more members than lichess. So in that regard if lichess had as many members as chess.com it would crash more often, too. I've been experiencing lag too, my hypothesis is that members with a chess.com membership get put on higher level; servers to provide them with smoother play to sell more memberships. Also note that chess.com gets new members (accounts) every few minutes.
Lagging Because of Ads?!

Chess.com (unlike platforms like YouTube) doesn’t punish adblockers. If your friend is certain that the ads are the reason why lag is happening, that can be a solution. Using the mobile app (which has significantly less ads) is also another option.

My friend claims to be lagging due to the amount of advertisements he is receiving on the website under the default (free) membership status, claiming that getting membership will help; which he doesn't want to actually get. Who else is experiencing this and is it really because of the ads or is it because of something else like website traffic? It doesn't seem to be happening to me.
Use a better os, use a better computer, use better internet. Then you will not have any lag. Most likely it's either the os or the computer.

My friend claims to be lagging due to the amount of advertisements he is receiving on the website under the default (free) membership status, claiming that getting membership will help; which he doesn't want to actually get. Who else is experiencing this and is it really because of the ads or is it because of something else like website traffic? It doesn't seem to be happening to me.
Use a better os, use a better computer, use better internet. Then you will not have any lag. Most likely it's either the os or the computer.
I agree, though how much do they cost anyways...
My friend claims to be lagging due to the amount of advertisements he is receiving on the website under the default (free) membership status, claiming that getting membership will help; which he doesn't want to actually get. Who else is experiencing this and is it really because of the ads or is it because of something else like website traffic? It doesn't seem to be happening to me.