The reason the third set of Earthspark episodes were such a disappointment to me was that I expected all the plot threads from the previous two thirds of the show to interweave and instead a lot of them were just dropped.

Like why did Optimus need to keep Bumblebee's existence a secret? Why did GHOST think he was dead? And what consequences did Optimus face once GHOST found out Bee was alive? Seemingly none. Optimus showed up so little in the second batch of episodes that I kind of thought they'd retaliated against him and imprisoned or brainwashed him but nah, he's fine and it's never explained why Bumblebee had to fake his own death.

What was the Cybertronians' war initially about? It is unbelievable to me that this wasn't explored. First, it's interesting! Second, it would give us insight into the motivations of the Decepticon ensemble.

The show is a sort of a "what if" AU based on G1, and in G1 the Decepticons were warmongers who wanted to rule the galaxy and enslave everyone. However, if you've read MTMTE you might notice Megatron chiding Shockwave for dismissing the Terrans as "lower class beings" and conclude that the war was about classism. But ultimately the viewer shouldn't have to fill in the blanks from other media. Earthspark should address this within its own show, because the question "Can the Decepticons be trusted, can they be redeemed?" can't be answered without it. Like, if the Decepticons were just The Evil Bad Guys then it wouldn't matter, but if you want them to end up freely walking the Earth then it's extremely important to know if the average 'Con's motivation for joining the army was "I'm standing up for my civil rights" versus "y'know, I just love killing people." Especially since, unlike the easy-breezy G1 cartoon, in Earthspark the TF war resulted in human injuries and deaths.

Shockwave and Soundwave's complicated feelings about Megatron never get resolved or even addressed outside their solo episodes. Which is very odd in a series that put such an emphasis on working out emotional strife, what with the cyber-sleeves and all. In the finale the Decepticons team up with the Autobots and Terrans because Mandroid wants to destroy all robot life: a purely physical threat. And that was a cool fight. But it doesn't resolve any of the emotional baggage. This disappointed me because the emotional fallout of Megatron's side-switch was the most interesting part of the show imo.

Then there was the Starscream episode, which felt like the "Dear Princess Celestia" moral in the last two minutes of a MLP FIM episode without showing how the conflict played out in the previous twenty minutes.

Earthspark got renewed for a second season. (And I'm glad! It has a lot of potential, that's why I was pumped during the first two-thirds!) But they thought they might only get one season, and if that was the case they would have left us with all these dead ends.