The things you describe are only Unleashed and later. Sonic Adventure, Adventure 2, Heroes, Shadow, and 2006 don't have those things.
SA1 and 2 don't have Boost gameplay. They stick to Boost gameplay because there is still a large amount of casuals who claim that all the pre-boost games were bad, and of course some of them were. But 2006 being bad made them throw out the baby with the bathwater, and change everything about the series, including the core gameplay, instead of just deciding not to release an alpha prototype again. Unleash still got flak for the Werehog, so they removed it, and then Colors and Generations got good reception (though I don't think Colors' was well deserved). Then they tried Lost World, which removed Boost, but frankly still played very much like Colors 2, but it didn't do well, so they figured they needed Boost (and Classic Sonic), and we got Forces, which was very much Generations 2 but without the polish that made it as good as it was. Forces also included more of a story, since I guess they finally heard Adventurefags complaining about the excuse plots since Colors, but it was clearly done by people who never played or understood the games they were supposed to be emulating, and it came off like a ridiculous Deviantart fanfiction, so that got bad reception, along with the rest of the game. So it won't surprise me if we just get more of the same next time, but if it was going to be something different, now is the time. People are still bitching for the Adventure style back, but since they fucked up with their awful attempt at an Adventure-style story, they might figure all the Adventure style stuff is still bad. Maybe we'll get a new thing. But we'll see.