I am not arguing the fact that the current building code, technology and quality of materials is much better today than even 20-30 years ago.
And, as many of you say, if you can pick the builder and oversee the construction process, you will very likely end up with an excellent quality home.
My argument was more around my real-life experience. I got married and we wanted to buy a house close to my in-laws and close to work. That severely limits the options. You either buy new or an older home. Mattamy was the ONLY thing available at the time in the area we were looking at. They bought this big peace of land by the Palladium that was under development. There was another once in Kanata Lakes but it was totally out of our price range. So we bit the bullet.
My biggest problem with them was not the quality of the building materials but the quality of work itself. There was huge shortage of trades and they were hiring anyone willing to pick up a hammer. It was truly appalling. Sloppy workmanship throughout.
At one point, I was at the site and saw, in the house across from mine, that they put the insulation and water barrier that was filled with rain water - literally tons and tons of rain water inside the wall frames. I took pictures and when I met the future owners, I told them I have evidence of this
and they should act on it. They had major problems with mold, among other things.
The engineered floor joist - while I understand they are cheaper to make and stronger, it allowed the builders to put them at 19" on centre instead of 16" for solid joists. The floor deflection was so bad, it didn't allow for ceramic floor to be installed after we moved in. Also, I have been told (hearsay, I know, but I believe it) fire crews would not go into a burning house with engineers joists because fire eats them so quickly, the whole structure collapses in no time.
In my house they didn't let the varnish on my maple stairs cure (40 steps, no less) and boot prints were all over the stairs when I moved in. They forgot to put in the rough-in at my next door neighbours and had to install it after they'd moved in. We all had new-borns at the time (there were like 15 kids under 2 on our tiny street). This is the type of quality I am talking about.
After 3 years there, the house appreciated by more than $100k, and we had had enough by then. We moved and couldn't be happier in our "new" old home.