In general what you are saying is usually true, however, although there are certainly more threads about all kinds of complaints, quite a few replies (sometimes even the majority) in those threads are from people who aren't having any issues and/or think iOS 7 is great or at least better, so in that sense, it seems like that group of people is not really all that silent nor a minority necessarily.
As for the dots and bars, it's one of the more subjective things, some might like it some might not, it doesn't really affect anything specifically in any way more than just preference. But given a discussion forum like this one, nothing really odd about discussing differences in something or something new.
Except there are those who bash the entire OS over something trivial like signal bars/dots.....
All-in-all, I'd say any complaints with iOS 7 itself are subjective. Any complaints related to performance issues are partially subjective, partially just complaints about old tech/technology in general.
In the end, I expect iOS 8 to refine the base set in iOS 7. Further UI refinements, big fixes and some additional features. Essentially, what updates 2-6 were before the big change in 7.
Every 6-8 years, people are going to have to have a little more patience. There will be a larger than usual update that may take a little longer to make perfect. Heck, we were on the 6th revision of iOS 1 (imo) and it still had its quirks.
These are some things people need to keep in mind when upgrading/updating:
(1) Battery life ALWAYS takes a hit immediately after an update. Go Google it - there are complaint threads for the last I don't know how many iOS updates talking about that particular update killing battery life. It works itself out.
(2) iOS 7 was NOT a typical update and should not be treated as such. Subsequent updates will be more in-line and normal compared to 2-6. Basically we get a big change, then 5 years of refinement, then big change, and so on.
(3) Newer devices will ALWAYS run better than older devices. And older devices will slow down no matter what software they are running. If you care about speed and performance, don't sit on a device that's 4 years old.
(4) Updating the software is always better than not. Give yourself a chance to get used to it. It's not that bad. And you gain additional features and fixes you didn't have before. There are tons of iOS 7 specific features I use everyday that I wouldn't want to be without now. Change isn't scary - just relax and tap "install".
(5) The MAJORITY (I'm talking 99%) will have relatively no issues with new devices or software. There are hundreds of millions of iOS devices in the wild. the million or two that have problems make up a VERY insignificant (statistically) portion of the consumer populous.
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As someone posted earlier, here's what you described in a picture, and while using words it was possible to make the "complex" one sound outdated and busy and an eyesore somehow, and make the "flattened" sound like some amazing new and great thing, a picture comparison will easily tell the opposite story no matter who looks at it:
Image
Right because a CGI gecko is the same as a felt pool table on my phone.....
Not even close to the same thing.