Why should bad designers get to force a bunch of people to fix mistaken web design choices?

"41% of 18-29 year olds polled said they use adblock ... In some countries nearly one quarter of the online population has it installed"

-- http://blog.pagefair.com/2014/adblocking-report/

That is a small number of people of the total Internet population.

It's a bit surprising that you think an advertiser pushing ads is a suitable source for information about ad-blocking. Obviously they're going to say that ad-blocking is prevalant and that you need to run better ads to stop people running ad-blockers and oh, we just happen to be an ad company that runs that particular type of ad.

There's apparently 2.9bn internet users, so you're right that ~5% isn't a very big number in context.