2) Bad to pick out MM4 as your example, as it had the most well-balanced weapon set of the series until 9 came out.
Yeah... I'm not going to say 9 had a bad weapon line-up per se but I find it bad level design to force usage of said weapons to progress, never once did I find use for Tornado Blow or Concrete Shot outside of using them to dull out some obstacle, and in the case of those [tornado fang]ing lasers in Wily Fortress 4 half the time the stupid thing would miss and I'd run out before getting to the teleporters. And even then I never found actual use in Black Hole Bomb, Magma Cannon, Plug Ball, or Jewel Satellite (Outside of farming for Telly drops). Hornet Chaser was good for a few things, primarily Angry Rock and Laser Trident was the best weapon in the game. Not that its saying much since I
loathe Megaman 9.
Also:
2) Weapons were useful, I can't recall many useful weapons in either 5 or 6 but I know 4 had Pharaoh Shot and the Drill Bombs.
I should point out that I really enjoy Megaman 4, its easily my favorite 8-bit right behind 3. I do find some weapons useful, but a lot of them were just not very useful to my playstyle (For example, I don't use barriers outside of boss weaknesses or for stupid [parasitic bomb] like Telly swarms, and some weapons are just too conditional to be of much use elsewhere.) Its cool and all that you can find uses for stupid [parasitic bomb] like Power Stone or Charge Kick or hell maybe even Centaur Flash but I sure as hell can't.