The settlement buildings you can only get once in your account life though, and even if you had just those buildings you wouldn't be competitive enough. If you came back after 4 years, you'd have a small QI bonus, sure but that's it. All of the event buildings over the past 2 years since QI got introduced would be missed. In the other areas you would be sorely dissapointed, you wouldn't be able to do trial 50 in any of them because the event buildings from 4 years ago arn't as good as they are today. If I need 20k%+ for GBG trial 50, these settlement buildings are only giving me maybe around 500%, that's like a drop in the bucket. The settlement buildings would help a little bit, but nowhere near the amount needed to be able to be competitive.
I would agree with you if people could get multiple settlement buildings like the items in QI, but that's just not the case. These items are what people worked 6+ months on each one to earn, and can only earn once on their city.
Plus, if inno is going to continue with developing settlements like the pirates, they really can't be leaving the others behind in their stats, although even these are waning on their usefulness.