No character is (at least isn't supposed to be) inherently bad at smash. Yeah, you have your tier lists, match ups and everything, but in the end, what counts is what kind of PLAYER you are.

Sure, Sheik has a kickass framedata, but why should we care? It's a fighting game, not an agility game. A fight is about using what you have in your favor, knowing your weakness and strenghts and using them in your favor.

Ok, marth may not be as fast as he once was, he may not have his kick as reach he always had, but try to look at what he DOES have: He can effectively have the power of a ganondorf or bowser with an above average agility, disjointed hitboxes and a smaller hurtbox. Sure, it can be mentally straining trying to properly space so you can land your tipper, but honestly? Smash WILL cause a strain if you try to play competitively. The only difference is that instead of being a mechanical strain (as in trying to apply a tech or a Sheik/ZSS combo), it is a mental strain as you try to control the space around you more effectively.

All characters have tools that reinforce their own fighting style. Smash physics and nature influence in how they can perform, but it's up to the PLAYER how effective it can be. You can't rush with a Ganondorf, but I'm sure you can land a monster hit with one if you don't mess up.

Marth has his strengths. You have your own. What you need to do is ALIGN them so you can be more effective.

And before you say I'm just trying to be a casual-friendly bystander, NO. I main marth, I like competitive smash, YES, I already got frustrated with some of his flaws, but after looking at him, I can't help but feel like he IS a kick ass character. down throw bouncing fish combo can just nullify a character like that.

Experiment. Train. Learn. Improve. Win.