This is a resource management game... That is pretty much the all of it.
How many Zeta's you got and spent then complaining about new toons needing Zetas is EXACTLY the point and issue in a game about resource management. If you spend every credit heist penny to level toons you won't be able to use in 2 years or will use once for fun, you are wasting resources and will not have the credits when you do need them (like now). Exact same principle with Zetas.
I had literally 115 zeta mats last week. I had nothing I needed to spend them on. I spent them on my first dark side/Empire arena squad. They are doing slightly better than the squad I already had on Defense but not 2 characters and 2 zeta farms.
I was/am disappointed, the resources that I put in did not pay out to the level I was expected. I could have farmed r2 instead and maybe had a slightly better team and been more prepared for the Journey.
At the end of the day it was my resource management mistake that put me in this position. I should have known better etc. Though like you (I would guess), I was more eager to try something new.
Trying something new isn't a bad thing, its just not the BEST min/max thing to do in this game. Just like farming and using toons you "like" isn't the optimum thing to do either.
You can't have it both ways in this game. If you want the uber toon immediately you have to wait, plan and ensure you manage your resources properly.
Sounds like you pissed away zetas imo.