Changi is a good airport. There are plenty of things to do, its clean, comfortable - never seems to be anywhere near full; there are things to eat, do & buy more or less whatever your budget. Plenty of seats & places to rest.
Most air ports are
They are purely passenger processing facilities.
Some are truly awful.
My local - Hong Kong regularly wins awards but for what I'm not sure. Yes you can reasonably expect your bags to be delivered within 30 minutes & you can take a train, bus or car / taxi to / from quite easily.
But it is dull. The shops are OK if you want to spend HK$16000 or more on a Tatty Handbag. It is now regularly rammed (as it processes mainland tour groups etc). If you are not a HK ID card holder it can take ages to pass immigration and going through security is hardly fast (but nowhere is these days).
I used to enjoy travelling...& airports but now it is mostly boring, dull and painful.
The terrible seating & lack of clean toilets in most airports adds a further insult.