On a technicality (which is what trademark attorneys deal in), your point falls to the same fallacy. The product Adblock is an "Advertisement blocking engine" or the like. "Adblock" is a made-up word and therefore likely eligible for trademark. (Or it was before the namespace got polluted with all the variants.)
"made up word" is overly generous. It's the word "ad" followed by the word "block". "ad block" is a valid description of what it does, equivalent to "advertisement blocking". You only put the word "engine" in there to fake there being a difference. Microsoft wouldn't be able to get a trademark on "Operatingsystem".
