Short version: temples stop paying gold for kills, and the fairness system got better at telling a real war from a staged one. If you fight normal opponents for normal reasons, nothing about your day changes.
A temple gives you a bonus while you hold it. That is what it is for, and that is what it keeps.
What changes is that fighting over one no longer simply pays gold for the troops that die there. Buff sites have worked that way for a long time; temples simply join them. Take a temple because you want what it does, not because of what the fighting pays.
The game already watches where your gold and experience actually come from, and quietly reduces the reward when nearly all of somebody's progress comes from the same arrangement over and over. That part is not new.
What is new is that it has become harder to dress an arrangement up as a war. Losing armies to each other on purpose, in a place where losing them costs almost nothing, is no longer proof that a real war is going on.
Nothing here is a punishment and nobody loses anything they already have. Rewards from ordinary fighting are untouched, and if you are simply at war with somebody who fights back, you will not notice any of this.
Most of you will never have run into either of these. A small number of people found that two accounts could earn more by arranging fights than by playing, and at the top of a league that decides who finishes first. That is not what the leaderboard is supposed to measure.
Both changes start with the new season, not today, so nothing you have in flight is affected.