Balancing civs is trivial, just have a unit type, let's say jav cav, be OP enough and make it available to all civs and you are done.
The above is a solution but it goes to show that balancing civs may well be undesirable or far from the only goal. So when is balancing even relevant and who is even qualified to talk about imbalance. Just recently I saw a match-up on yt where a much better player beat a weaker player and the conclusion of the commenter was civ a stronger than b. In my opinion the game would have ended the same even if you doubled the gathering rate of b by a factor of two and reduced build and train time by half.
Except for pro players which can constantly play a good game a good run vs bad run is far more relevant than whether civs are balanced or not. I mean what's the point in talking about balance when you struggle to even reach pop cap 25 minutes into a sandbox game? So let's assume we have two players both able to reach 300 pop in well less than 20 minutes, one knows to dance the other not. Balancing civs is still irrelevant.
My point is unless you are one of the few who know to use and abuse the game at it's limit you shouldn't care. What do those 2 or 3 dozen players which can be counted as pro players need for the game to be interesting for them as well? A few none identical civs which each supports multiple strategies at roughly the same level will do just fine. If for a release a certain civ is considered game breaking just ban the civ by convention from rated games or tournament rules and be done with. For rated games enforcing mirror match-ups on balanced maps might be another way.
Going back to the original topic, why force tiers in the first place? If we check the earlier linked video those tiers appear naturally. So the act of introducing official tears with support in the code can be considered an act of over-engineering.
The release cycle is also a reason why you guys face such pressure regarding balancing. If it goes wrong it will be wrong for the next 2 years or so. Let me delve a little into what I consider wrong about the release policy as it may be called.
Alpha means it builds and runs for the most part. Basically what trunc should be at any point. Just any snapshot after minimal testing is worthy the label alpha. In my opinion a reasonable version scheme would be a major of 0 to indicate the intent of further enhancing the engine and getting rid of some major issues. Then the minor for the next release would be 24 and patch level 0.
So the next release would be 0.24.0. There can be an alpha/beta release thereof. If so feature freeze trunc and publish the binaries and source release and give user and packagers time of like 2 weeks to report release blockers. If appropriate tag the release and create a release branch. Then do a patch release once it's evident that game balance is screwed. Other than balancing changes apart from the obvious bug and security fixes there can also be changes to art or even new maps could be added. A patch release just mustn't break mods.
To sum up, there only needs to be a subset of civs that can be used for pro players in competition, which can just as well be empirically determined after the release and balance issues should they crop up should not be cemented for such a long time.
Well, I spoke a lot in little detail about a rather complex topic but hope it a least shows a different possible take worth discussing.