I think much of this issue is a lack of understanding about what exactly constructive criticism entails. If someone posts in your thread comes in and posts that everything is perfect and nothing needs to change, they are being destructive to the project, there are always improvements that can be made to anything and we shouldn't hold back to be "nice". If we were to limit ourselves to wholly positive comments we would essentially be telling people that there is no need to be flexible, that they can do no wrong. The tree that survives the storm the longest is the one that can best bend with the wind.
I'm not saying we have to go around with the purpose of only spreading negativity, but honest comments that bring up issues are orders more useful than an empty bit of phrase. "Great game, can't wait to play!" is essentially an empty and useless comment, while something along the lines of "Looking good so far, but I think the sprites are a little too low in screenshot 3," actually brings up an issue that others may have noticed, but would have gone unchanged otherwise.
While I have seen the community go through many changes - likely more than most who still visit, as I've been here for over seven years - I don't see the sense of community declining in any appreciable amount. With there being fewer "big" projects, there is a lot less for people to comment on, so people either focus their attentions on trying to improve projects with criticism or with positive reinforcement - the Supporters and Criticizers mentioned by Atomic Reactor above. The only reason this division seems to be more sharp than in years past is that there are less people entering the community, so there haven't been any major shakeups for quite some time. This isn't to say that more members would change anything in a good way, back in 2007/2008 we had a huge influx of new developers, most of which settled on making games that were incredibly homogeneous, also creating a sort of static community.
I think the issue with ego is that many have difficulties being objective about their own project. It's understandable that a person would have an emotional connection with a game they developed, but that connection does not exist for people commenting on the project. I honestly don't give a crap if someone spent eight weeks or eight minutes working on something, if I see something that could be improved it deserves criticism. Everyone should be able to feel proud of something that they made, but there shouldn't be any hurt feelings or anger when others find it less than perfect, that's life.
Now, I'm going to do a quick sample critique of this random map I found.
Honestly, it's pretty awful. You've almost copied Pallet town whole cloth, making for a pretty bland map. It isn't helped that you've chosen to use RSE tiles in a map primarily using FRLG tiles, and the clash is pretty extreme, with that tree in the center standing out particularly badly. In addition, the path you've included doesn't make much sense, surely there would be more foot traphic nearer to the lab than the houses on the left? You also need to expand the map to include a "border" of several trees on every edge so the player character doesn't walk off into the abyss or some such.
While all the comments I made were pretty negative, they all pointed out flaws in this sap's map that anyone would notice immediately. Some might argue that there should be a positive comment slipped somewhere in there, but that's not my style - it's a pretty terrible map and I feel that complimenting something in it would muddle the intention of the critique - which is that things need to change.
Feel free to respond/curse with blackest sorcery.