> first and foremost informs
I'd claim any extent to which ads inform the viewer is downstream of the ultimate goal of having people spend money on the product. The company behind the ad does not inherently care about you being informed, just that informing people (in very selective ways) sometimes happens to be an effective way to increase sales. Where it better serves their purpose to misinform, that's what they do (which legislation can help curb).
> Remember the time you learned of a particular programming library that does the thing that you wanted to do?
Typically by searching a package index, opposed to someone being paid to shove a product in my face unsolicited while I'm trying to look at something else.
I don't think it really helps defend meaningfulness of the job in question ("techy, working on serving ads") to expand the scope to considering other things (writing package documentation, reviewing tourist destinations, ...) and then point to the fact that some of those other things, which the employee in question doesn't do, are useful.
> Why do you drink (coke / pepsi / fav. brand of tea / fav. brand of coffee)? What formed your opinion was some kind of marketing, either directly, or indirectly.
Being persauded to buy one sugary drink over another (or over water) doesn't really seem to be a constructive outcome, especially for all the time and resources wasted. Actual information incidentally gained from Coke ads is little to none - you'd be far better with an independent review/comparison.