From a game design perspective they are weighing all the factors and I have often speculated what the mind of the designer is thinking.
I can understand how initially, they were reticent to adjust smash4 Samus, if you simply write things down on paper she has a lot of things going for her.
Very heavy yet not the slowest, high combo capability, fastest and powerful f-smash, multiple projectiles, highly damaging kill projectile, shield breaking options, tether recovery, z-air, good even great tilt range, good damage (really good in combos), invincible out-of-shield up-B, several kill moves beyond smashes, multiple tech chase starters.
So then they try and balance it out, and from the design perspective it's clear: bad jab. This character cannot have a good jab. Throw them a bone if they manage to severely damage their opponent.
Likewise set in stone: this character cannot have a good grab. If they land one, throw them a bone with some combo potential out of it.
Worst roll. Punish this character for rolling away. A good roll would circumvent bad jab and bad grab, can't happen.
Terrible up-smash, terrible d-smash. Make them the worst in the game.
Add cooldown, lots of cooldown. She's a heavyweight, a super-heavyweight, cannot have moves with no cooldown. Particularly given fast startup on attacks.
No disjoints, the player of this character must be super precise, no excuses, skin tight hitboxes and hurtboxes right beside each other.
Floatiness I think in the designer's mind is beneficial, not detrimental. I'm pretty sure it's seen as a positive.
Where things went a bit wrong in the balance equation...
Rage means anyone can peform d-throw -> up-air with Diddy, because the range of applicability is literally 30 -180% with rage and DI factored out. Much more narrow range combo like up-tilt -> SH CS is very much more difficult to land because the % are always changing. No one, aside from loons like me are actually going to go to the trouble of training to add 1/10th of Samus' damage to the opponent's damage mid-match. Yes the payoff is destruction, but it's painful.
Teching grounded meteors, I'm not sure when that decision was made but I still think it's wrong. Very wrong. This is smash, we like to see things bounce around the screen, even the most casual of players. This is a terrible decision and it hurts Samus more than any other character.
Too much cooldown. Just too much. Particularly missiles and grab...
Skin tight hitboxes and proximity hurtboxes, simply too skin tight relative to rest of cast.
Again, I absolutely love playing this character even as is, way way way more than Brawl. I see many decisions set in stone, that are likely not to change. Others, really could/should change and may not be critical to design intent. If they do change something my bet is again teching, (some) cooldown and maybe maybe hitobox/hurtbox modification.
I for one am a bit frustrated by f-tilting into Sonic's up-smash and having his multi-hit not only out-prioritize me (makes no #$% sense) AND fully drag me into it from the extended portion of my leg. The same does not happen with my own up-smash, not even close.
I'm fine with "to land XYZ with this complicated character and blow them away you have to be really good". In fact I will always gravitate towards that type of character. I'm not fine with "the brain-dead simple always has advantage".
Incidents like that make me question the design. I'm not sure that's design intent, if it is truly the design intent, I really want to hurt someone.
