Samus seems great on paper, I found the same thing when I started out with her; why does this character with so many great aspects come so low on tiers?
Basically it comes down to a few things, samus can't really shield grab. That may seem minor but it's actually pretty significant, yes she can UP B out of shield but the inability to shield grab attack leaves her at a substantial dis advantage.
Another factor is her seemingly amazing projectiles, the top 6 have methods of dealing with them. Marth/Sheik can easily swat them away, Fox/Falco can reflect, Peach can clank them with turnips and Falcon struggles more at a distance but if you are mid range from falcon shooting missles it's an invite for him to approach you.
Also when you start playing higher level players you wil get combo'd, she's actually really easy to combo because of her floatiness, just not in the same way as say Fox/Falcon is easy to combo.
I hope that clears things up a bit for you? I don't know whether people would agree...but anyway just btw I mained Samus for a long time but I found her really tough to take on the higher standard players with and switched to fox/peach.
I most definately agree with this, (samus actually has the matchup advantage against peach) the reason she's at the top of mid-tier and no higher is due to her lack of shieldgrab but also the fact that her roll doesn't go very far and does so very slowly, compare this to shiek who's roll is useful or peach perhaps and lets place them against a fox who's drillshining the crap out of their shield, samus can shield upB really easily to deal with shield pressure like this... but fox will hit the ground first meaning she can usually get punished without ledge cancelling or landing on a platform etc.
Peach on the other hand could roll, short hop an nair or shield upB or if she has inch-perfect timing perform a shield grab
In this instance Samus has only ONE option to avoid punishment and when your opponent knows your only option it's easy to bait and easy to punish, her lack of shield tactics are what push her down in the tier list - Samus has extreme capability in every aspect of the game other than this, she is the 3rd heaviest character (4th in Pal) has the most versatile recovery (which unfortunately can be gimped by jigs and occasionally sheik or peach) she is floaty and therefore extremely hard to combo (falcon gets auto combos on her cuz of this) and even has an auto escape method from the IC's chaingrab (not edgechaingrab nobody can get away from that) So she's great on paper... but oh what's all that in the brackets up there the exceptions to the rules which make her so wonderful, yeah she has good matchups against peach and IC's goes alright against jigs but most of the top 8 characters have something they can exploit, Samus who is used to control the stage and force people to approach loses this edge against fox, falco, sheik, link and younglink all of whom can force HER to do the approaching, against peach or jigs they can simply avoid all her projectiles all day long and outdo her on aerial mobility and recovery speed...
The tier list is in place to demonstrate character potential, the potential to be awesome with that character and how much ease one can do it with; the higher the character the less gaping flaws they posess or the more auto-combos etc. to quote a famous Samus player "tiers don exists" Samus is as good as you'll make her; she has all the right tools to **** around with anyone and win but you have to play it smart and compensate for her flaws (use her broken backward wavedash out of shield) if you've ever seen HugS play then you know that this can be done and used to beat the top players of any character... except Mango
But to address the topic of the thread once more her position on the tier list is where it should be, it does not indicate her worth rather her relative ease of use at a high competitive level as opposed to the characters above her if you've ever seen Taj or Axe play then you'd know that a character is only as good as you make them.