you got me there, Evan. I can personally see where the level design and the mechanics and the character design all mutated from, and I can appreciate this game quite a bit. I'm going to chart it, not nessesarily defend it.
Naturally, starting as a sonic fangame, level design was something Strife wanted to nail first; having that multi-tiered level design that both had the hits of exploration the likes of Sonic CD, S3&K, and Sonic advance 3 had going on was something he wanted, but he wanted to take out things that constantly break the flow of that. that's why there's almost NO instant death pits or enemies or asshole spike locations that actively grind the game to a halt.
Somewhere along the line, the idea of Dr. Eggman Bossfights came up, and usually those tend to be... piss easy to outright bad and non-engaging. This is where some of the Treasure inspired ideas for mini-boosses, mid-stage bosses, and end bosses come in. some of these are pretty overt such as the 7 Force inspiration with the boss fight with syntax at the end of Final Fortress 1 or the Serpentine mech from Fortune Street 2 being a direct riff on a Mischief Makers boss.
Sonic Romhacks and fan games were finding ways to impliment all sorts of moves into the sonic games in the same way that Sonic Advance trilogy and Sonic rush did, trying to give Sonic a spin dash, the super peel-out, Insta-shield, a double jump, and a homing attack all on the same 3 button genesis controller control schemes. usually, players of these titles would have an easy enough time exploring the controls and figuring out what's what among the community that frequent things like Sonicretro.org or the Sonic Ameteur Game Expo competitions, which Freedom Planet was entered into the 2012 SAGE competition. In this bubble, Lilac's Sparkster style boost and (at the time) normal spin-dash along with her kick attacks were well recieved.
However, the devs then decided they wanted to take it away from where they'd actually be infringing on Sega or be tagged as a fangame, and so further things were tweaked and in their core group of QA testers, things seemed to be going swimmingly. the levels stuck to the core ideas of being clearable by all the characters, who felt distinct yet comparable besides the stages later in development made specifically to highlight abilities exclusive to a character. More of the Treasure style batshit insanity was put into stages like Battle Glacier and the final dreadnaught stages, but designed in JUST such a way that because the enemies don't do contact damage and have windup before they spray bullets everywhere that you can mostly speed by the most threatening enemies, and things kept shaping up for their small but dedicated QA team, which probably consisted of people who were part of the target demographic for this game anyhow.
I mean, not that getting the Sonic Adventure style furry drama there wasn't a priority either, because it totally was... not to mention getting sprite artists who could properly realize things. if you look at that old SAGE2012 demo of Dragon Valley, it's looking a heck of a lot more... flat than it does in the final product when they hired more sprite folks.
I don't think Strife expected Freedom Planet to do as well as it's done... not to mention it was pretty much Galaxytrail's first game as a company. I'm surprised they immediatley were like "YEAH FREEDOM PLANET 2!" instead of goingg to a different project, but... yeah.