You must have had some terrible experiences, and for that I'm sorry. But you can't stop people from doing that regardless of whether add-ons exist or not, they're still going to find a way to shove their elitist attitude in your face.
Personally, I used damage and healing meters to better my skill in the games I've played. If for some reason my parses weren't stacking up with others of my class/spec/gear level (which also having that comparison to make is ALWAYS nice) then clearly there was something I'm doing wrong that needs to be improved on. To me, its frustrating not to know how well I'm playing, if I'm maximizing the output of my abilities, and utilizing cooldowns and buffs the way I should. I shouldn't let those I'm playing with suffer either because I can't be sure what I'm doing wrong without properly gauging my mistakes, and meters in particular help me do that. In short, I don't expect people to hold my hand. I'd like to know myself, so I can improve myself (or ask someone who is clearly more experienced with my class to share their opinion).
In my general opinion, add-ons are something that I would like to see. Having looked at how the raid frames setups are, I am already frowning because the player frames are on the far left of the screen. Yikes. I would definitely like to see if nothing else, ui addons implemented for customization.
You can't blame add-ons solely for the community changes in WoW. For as long as that game has been around, the fluctuation of community interaction has changed drastically from year to year. Also, competitiveness is a part of any game. I feel you're making comparisons that aren't fair. You can't compare this community to that of WoW. You can't assume that just because there's a chance that add-ons will be implemented in this particular game that the outcome will be a rise of elitist jerkwads that will "ruin" the game play experience. And honestly, even if add-ons aren't implemented, its like I said before, if someone is going to be "I'm better than you" they won't need an add-on to say/do/show that.