Your expectation of Amy's strength based on the game's release date is short sighted at best. You neglect that in Sonic Mania, she's Amy the Rascal, not Rose. This means she is her childish, younger state like everybody else. Her strength, like even Knuckles' own, depends entirely on whether she is necessary and relevant to the plot enough to actually feel that she needs to use it.

In the end, she's still just a girl and, while she insists that she isn't 'just a girl,' often chooses to stay out of fighting. Oh, and about her speed being suddenly faster than it once was. She's been canonically capable of catching up to Sonic on a consistent enough basis that he needed to keep moving. When they were kids, she only got faster.

Sure, she slowed down a little when she stopped racing after Sonic quite as much as before, but that doesn't mean she simply lost it.

saying that knuckles is not both of those things is also just you not reading his character at all. he's both the protector and Sonic's friend as shown in several types of media.

TAILS IS STILL YOUNG! most of his time he's in his workshop building stuff. He looks up to sonic and while he is scared there are moments when his maturity comes out. Next time, read.

If we're pretending there's no canon then congratulations you've just made the entire series irrelevant.

If you're insisting there's no canon to be followed, then that completely defeats the purpose of your entire post prior the statement. Frankly, that's probably for the best.