Is the champion OP or does the current game simply favour them?

Generally I find that there is a new OP champion/s every time a certain change is made to the game. It's not always that this champion is inheritable strong its just that changes to items/maps/structures and objectives makes them become so strong compared to everyone else.

I'm going to give 3 examples of changes that resulted champions becoming overpowered (or more overpowered than before)

The 3 changes are:

1. New Jungle

2. Mana regeneration nerfs on items and champions

3. Removal of DFG.

4. New Jungle: With the new jungle monsters becoming tougher and the junglers always being behind on gold and levels from farming, champions that get money from early ganks or excel at them became even more prominent. and are all you see nowadays because they have the ability to make early ganks and snowball games. They have less reliance on ultimates like a or a and have easy sustain in the new jungle as compared to our poor tanks

5. Mana Regeneration Nerfs Assassins are dominate in league pretty much the story of season 4 and looks to be the same for season 5. Anyone without mana is immediately superior in their roles again, or any energy user has such an easier time sustaining in lane and therefore being able to leave/roam for objectives without going oom. Why do you think we only see and in the top lane in LCS, because they have resources/passives that help them solve the mana crisis.

6. DFG removal Good god. Goodbye and AP assassins. You guys are now weak mana hungry long range mages like the rest of the unviable lot. "Mana-free Assasins forever!" Riot 2014-present. In all honesty theres a reason why is rising to prominence in ranked. Without the DFG mages can't 2-3 shot burst the assassins (which they need to be able to do to survive) and they can't Shred tanky midlands like a decent Swain.

Now some of these champions may have been OP before these changes were made but most weren't and soon they'll end up getting nerfed into obscurity all because we keep changing the game before realizing what those changes will do to our champions and the already major lack of balance and diversity. I mean remember preason ? How the hell did no tester or designer see that coming beforehand?