they removed slide and charge shot because they seem to think that megaman 2 is the greatest game they ever made.
Not that I hate MM2, but it's not the greatest MM game ever made to begin with (I personally think MM3, along with X1 hold that position).
If I recall, both slide and Charge shot made stage transversing and boss battles rather... easy. Mega Man being about difficulty (I assume...) was what made fans enjoy it so...
Well, how do you think that easyness can be solved? A trickier stage layout and stronger enemies/tweaking the Charge Shot. That could've been easily made. And you're right about what MM games are about: difficulty and how you solve it.
...the only thing hard about the mega man stages were the enemies themselves since they gave off that feeling of intimidation (big eye anyone?).
Nnnnnooooo... the stage layout is really important, since it can also determine the type of enemy that can be implemented into the game to make things more difficult. The stage layout is not only the look of a stage: it's the enviroment itself (platform-ladder-pit-hazard positioning, stage gimmicks...)
A MM game can be very different if the developing process follows the "design neat and useful weapons/abilities->make hard stages that encourage the player to use those useful weapons we designed to beat it" formula, instead of "make hard but beatable stages->design weapons that make certain parts of a stage easier". I believe MM5-6-10, X5-8 and the ZX series were made using the last method, making less emphasis in copy weapon usefulness.
However, I feel MM9 put more emphasis on alternate weapons than ever.
Remember MM1-2? I absolutely agree with you on that...
I went back and played MM5 and MM6 after playing MM9 and MM10 and I found that having no slide and no charge made things simpler without detracting from the experience.
...but not on that. Longer stages/smarter bosses would've easily compesated the addition of the slide, while stronger enemies/nerfing would've solved the Charge Shot issue. Capcom's obsession with "keeping it retro" didn't need to eliminate Classic Mega Man's most famous abilities, and they still did.
"Let's make a new MM game, but without the slide and the Charge Shot" is pretty much saying "let's hack MM2 and add new weapons". Don't get me wrong: I love the return of the 8-bit graphic style, but damn...