I think some of the rewards are great. At highest level you can get 5 hours of speedups per day (which is a > 20% increase in speed), you can get an extra 10 troops in your alliance army... I think these are very valuable boosts and I'm happy to pump in resources that I wasn't using anyway to get them.
The game is pretty good as solving the problem of having money sinks for end-game things, i.e. things that are very expensive, but give you some gain & something to spend resources on rather than resources just over-flowing. It also is good in that not everybody, or every alliance can have everything in the game. Those who strive hard will get small, but relevant advantages, and most people will have to specialise... you can't control if the base you're going to attack has artefact advantages that will nullify the formation of troops and attack style that you've chosen to use. It means there are lots of different play styles, which is good as far as I'm concerned.