In an ideal world opting out should minimize that data collection, although yeah I agree it probably doesn’t.

That said, I’ve done plenty of advertising analytics work, and some of the services (no idea about Reddit, I’m thinking more b2b than b2c) do offer the ability to analyze targets that matched your lookalike audience by whether or not a impression was made - meaning if you have ads blocked and never saw an ad, you may still be included in campaign results given to a third party even if you never saw their ad. That’s where the data collection becomes extremely problematic, as long as they have that tracking data to be able to classify you, you’re being included in targeting and targeting results given to anyone willing to pay for it. And again, hopefully as an individual that’s somewhat anonymized (is it? who knows), but I can say in the business advertising world it absolutely is not, I could take a list of targeted companies and feed them into further campaigns, even on other platforms. And especially in the consumer world, many of those advertisers are data brokers themselves, compiling and selling those results to increasingly sketchy companies looking for lists of contacts for who knows what.

Data has become this grotesque ouroboros in our economy, it continually feeds a never ending loop of advertising dollars thrown into the void, billions of dollars and who knows how much compute time, energy, emissions, with no real tangible output - but everybody is doing it, so everybody needs to do it to look like a competitive business.