Yeah, a good player will be able to do both. But I think he is saying that the current meta heavily encourages bad play, or at least, it encourages people to learn the advanced stuff before doing the basic. New tanks should not be worried about damage. Even a lot of veteran tanks shouldn't to be perfectly honest. If you can't do the defense stuff properly, trying to do the offense will just make everything so much worse, and we currently have a community filled with a lot of the latter. Part of it is just people being bad, but another aspect is the meta/community as a whole seemingly judges tanks on DPS right away without paying attention to other stuff. When that's all you see it's easy to forget the basic, more important, part of the job.
As for engagement, either you missed his point, or I fabricated one in my mind. Either way I'm going to talk on that point, that DPS doesn't need to be the only way to engage a tank. Right now the only other option is just to keep aggro, but it doesn't need to be that way. They could build tanks around lots of skills focused on predicting damage or reacting to it, or in other words make mitigation the engagement rather being the braindead system it is now. PLD was the most boring class ever in 2.x, most of the fun I had was it was doing stuff like flashing just before a table flip in Titan HM to try and a get a dodge, using stoneskin right before a tank buster, using cooldowns as early as possible to max mitigation time (or even cover two skills rather than one on certain fights).
This is what I wish tanks in this game were about. Make it about skillfully surviving, rather than basically just being a dps with a button you click every now and then and pray healers keep you up. I really don't play tank to be a dps. I will continue to DPS for sake of group and the fact there is nothing else to be doing, but it's not my ideal scenario. I don't think I'm really good at tank DPS to begin with, and my natural attitude is always to make things easier for group/healer rather than harder. But the current meta is pretty much built around pushing your healer's limits as much as possible while you dps.
Both healers and tanks who refuse to DPS are being lazy, definitely. I just don't blame them for the original sentiment of not wanting to do it. Because it doesn't need to be the only answer, and a lot of players legitimately play these roles because they don't want to dps.