My way of thinking is that "the problem" is when the stage significantly takes away your options, because this can create imbalance. Like in the example I gave for Pokemon Stadium 1, the vertical walls prevent you from approaching me from the front, potentially making the ability to camp too strong. Similarly, the claw on Halberd is a problem because it strikes so fast. The only way to avoid being hit is to air dodge or shield, but the opponent can cover those options for a free hit (also, unlike the Cannon and Bomb, it's impossible to use the claw to your advantage).I think the general concensus is that the entire part where the ship attacks you is a problem, and that only removing 1/3 parts isn't helping much.( at least here anyway as they can remain CPs for all I care in Brawl.)
The Cannon isn't really like this, though, there's loads of ways to avoid the laser. After it locks, it takes a moment to fire, so as long as you're moving you won't get hit (unless you get hit back into it, at any rate). Ditto the bomb. It always lands in the same place, comes out real slow, and a large part of the stage isn't affected, it's quite easy to get around it.