If the ad blocking ability of manifest V3 extensions is a poor version of what you could achieve before the change, it might make people look at alternatives such as Brave or Firefox where Ublock Origin will carry on working to its full potential. So it might be a good thing to end the Chrome monopoly on browsers.
I think Googles recent ad block detection on Youtube which stories about have now reached mainstream news site not just tech site like the register, has made more people aware that you could block ads online, As I have had a few people who are not technically minded come and ask me how they can block ads after seeing articles about it on news sites.
So it could end up being a Streisand effect at work now that Google tried to stop people going on YT with ad blocker extensions its made people who weren't using adblockers actually want to try them.