Yeah, I think they need to take a 'Generational approach' to the franchise. As in, if you will be making this a yearly/biyearly thing, have a plan. Mario does. Here is how they approach this: Mario 3D World, New Super Mario Bros, Super Mario Maker, etc.
While I do think that Mario franchise has sorta also peaked after Galaxy 2, thats because the team hasn't made a 'main franchise title' in that long, but I don't feel like the games they did between now and Galaxy 2 where all trash. I feel like their all each their own tiny experiences and I don't have that 'Well, that wasn't as good as Galaxy 2' taste in my mouth due to the game NOT trying to be Galaxy 2.
That's the thing with Sonic, the side games are trying to be a full game and turn out not to be of high quality. Why are you funding 20+ million for Boom games that are terrible? Get a fraction of that money and get Sumo to do another Sonic & SEGA Racing title. Am I crazy here?
Have a 5 year plan, a head of time, with 2 year + development cycles on each game that spans different genres. SEGA already hit the kart market and did well, I see no reason to stop that.
I think the issue has been, with Sonic, the lack of supervision. It feels like SEGA just expects games done when they say it and wouldn't delay them in the past. Look at Sonic the Hedgehog 2006, that shit needed like another year in development. Would it have been amazing? Nah, but it would have been easier to digest and the people that ate up Sonic Adventure 2 would have loved it.