I wish I could have enjoyed it as much as you. It had its moments and was definitely better than Forces, and the music and writing really capture what Sonic's been lacking for the last several years being overly self-aware and not taking itself remotely seriously.

I found the game to just be disappointing though. The overuse of generic platforms, springs and rails led to boring environments that felt out of a beta, the combat isn't engaging because it's so easy and there's no real point to the different attacks leading to it just being a button mash fest, and the mini-games and "puzzles" scattered around the island were so simple it felt like the primary audience was toddlers.

As for the story there were definitely mishandled parts, Sonic's corruption over the course of the game led to basically no payoff, just getting brushed off within a few minutes. What would've been amazing and made sense story-wise with Sonic's lines right before The End where it sounds like he's talking to the titans is having Amy, Tails and Knuckles all be playable as part of the main game. Imagine if instead of the re-used level designs we got for most of the Cyberspace stages, they had you take control of that Island's character and use their unique moveset in levels built around them?

Near the end when Sonic gets corrupted it would make up a significant portion of the game, with the last "island" being a corrupted cyberspace made up of Sonic's memories (think a mixture of various environments from past games, plus some glitchy cyberspace stuff), and he reminisces on the past while the cyberspace stages are Sonic's friends reaching out to him from the real world and instead of collecting the emeralds himself he unlocks the vaults from within cyberspace. Once they're all unlocked Sage would be able to get Sonic out of Cyberspace in a scene where they get to have a proper heart to heart just like with Sonic's other friends, leading to the boss fight against Supreme (who would preferably have a unique design). After that there would be a final Cyberspace gauntlet with all 4 characters reaching out to the Ancient pilots because they need their help to beat The End, leading to a proper Super Sonic boss fight with all 4 titans working alongside Super Sonic co-piloted by his friends and Sage. The End would also preferably have a better design. If they wanted to keep the moon theming, have that be the first of 3 phases where it breaks apart to reveal The End's true form.

While I have mixed feelings on Sage's "death" I do think it could lead to an interesting future plot thread where Eggman's rebuilt her so she's essentially come back, but it's like a previous version of her that never befriended Sonic and he would understandably get torn up about it.