I used to be [tangentially] in this biz, there's 2 things that will help a lot.
First, sign in, both on the forum and in your browser. When you're completely anonymous, revenue per ad is extremely low, so many extra ads get injected into each page in an attempt to break even. You might think they'd do that regardless to maximize revenue, but it's not true... too many ads just annoy everyone (more than usual) and lose money on average. But there's less concern about annoying the people they get virtually no revenue from.
Second, if you don't like a category of ad, you can often change that directly.
adssettings.google.com is a good place to start, and provides info and links for other ad networks. You might be creeped out about how much the algorithms have figured out about you, or you might relish the opportunity of filling your feeds with ads that are potentially more interesting to you. Or both.
The general theory is that, the more targeted an advertiser can be, the more valuable it is for the advertiser, the more money it commands for the forum (minus the ad network's significant but not extortionate
cut), and the more you get to see ads for new 4x4 pickup trucks instead of Barbie Fun Castles. And in theory, your synthesized, anonymized profile is only seen by the networks' algorithms, not by any humans and not by the advertisers. I trust this is true for the major players from personal experience, but there's a lot of shady operators out there too.
This is just FYI, I don't want to start a debate about privacy, surveillance, and the power of giant multinational corps, and won't respond to such. It's just spitting into the wind. Like it or not, this is how the modern web is funded, as time and time again the vast, vast majority of media consumers have preferred "free" to "not free". Use ad blockers or anonymizers if you want, I don't have a dog in this fight.