You're not wrong. There was often a short span where training droids are the limiting factor, but credits quickly become more of a problem. It seems that one aspect of that (that's likely unanticipated by CG) is that the period where training droids are an issue starts earlier and likely lasts longer.
If you're levelling a bunch of toons and running out of training droids b/c you're credit rich likely there's a couple things going on:
1. You're not spending enough credits on mods. Mods eat credits so fast it's hard to explain. You need to be farming and levelling mods to L12 very frequently, and then selling the ones that don't have speed or that are purple/gold and don't have adequate speed. There are special characters for whom speed is dramatically less important, but unless you're specifically trying to mod one of those characters and you know exactly what set bonus, shape, and primary you want, you shouldn't be keeping low-speed mods. Farm them, sell the junk, blow through your extra cash in a heartbeat.
2. You're not buying enough gear pieces with your raid currency. Carbantis and stun guns and Mk3 Holo Projectors are all in relatively low supply even at end game stages, and in the beginning you should also be buying Mk5 Fusion Furnaces and a few other things that are easily available with Mk1 Raid Credits.
Don't forget that there is ALWAYS some limiting factor on your progress. That's how the game works. Which things limit you change as you move through stages of the game. While the Training Droid shortage is real for you, it's not something that lasts. Toons only have to be levelled to 85, and as you move through the beginning stages of the game you're picking up an insane number of character shards. If you're finishing Galactic War every day, it takes only 11 days to take a new character from 0-shards to 330/7-stars. And of course, you're also gaining shards through bronziums and GW drops and Galactic Challenges. Someday those shards will all be for characters you already have at 7 stars. When that day comes, the shards get converted to shard shop currency and you no longer need more training droids every time you collect 330 shards.
But right now, you're opening characters at a fantastic rate. Ion the past you would have been short both Credits and Training Droids. Now it's just TDs. But that's okay. It's a passing phase. You can help yourself by determining which characters are most to your advantage to level up, but there's no getting around the fact that TDs are going to feel very scarce until you stop opening new characters every couple days.