I understand your position, believe me. I partially agree... But there is one thing to keep in mind, if the developers were limited to not making radical changes to their game with the aim of improving it as much as possible, just because this will alter the rules of the game and consequently affect those who have invested more. They would do absolutely nothing.
If we go to the point of view of "Gameplay" have made a wise decision, allowing large investors to destroy everyone with their Roman Legions would make very hard to maintain the user base that would make Rage Quit after considering it a case of "Pay2Win". With this system, battles are given a strategic factor, limiting the use of troops and at the same time presenting multiple different units to create a really efficient Death Squad that is not just limited to Spam as much Gunmen as you can or something like that.
To be honest, I don't think investing real money in Troops was a very good decision, for two reasons:
I have no idea what the combat system will be like, even before this change.
There are many blocked units so investing now would be dangerous because I run the risk of my troops becoming obsolete or inefficient on their own.
In any case, it is still a hard blow for those who invested heavily in the mechanics and in the game in general, personally I would be more upset with the fact of changing the rewards than with this... But of course, it's relative, it depends on the size of each person's investment, and it's respectable.
I hope you can get your money back as soon as possible man, Greetings and see you "in da steet".