You can do it, but it’s not done commonly. The most common way ads get onto the page is by including a third party script which is easily blocked.
Today, but this entire discussion is about how things will work tomorrow.
It would be easy to implement server-side rendering, but it carries significant cost in processing time and networking. If they can block all adblocking browser extensions by abusing WASM, the cost of server-side rendering will outweigh the 0.0001% of people that have a pihole set up.