Up-b out of shield is better than you think. Many times that you do it, it is highly likely to hit, depending on the read that you have on the opponent's shield pressure, or simply if they do something laggy on your shield like an early aerial. It's harder to smash DI than people say, in practice. If there are platforms you have the option to land on them, fast fall through, or even ledgecancel. It's invincible on startup ...
WD out of shield isn't bad? You make it sound like it's barely usable. Please watch HugS or Plup in literally any matchup. WD out of shield is a bread and butter movement option for getting out of pressure, especially with Samus who has a 14 frame WD (the fastest possible WD). The vulnerable part of the wavedash is irrelevant as long as you react to your opponent's movement/pressure strings. If you do it YOLO and they read it, then you deserve to get punished like any other option that gets scouted out. It doesn't lose to Marth's d-tilt. You can just wavedash back after the d-tilt. E.g.:
https://www.youtube.com/watch?v=9lT-nWpdWPw#t=0m57s
People are stupid for getting hit by ICs SH uair because they literally just don't consider that option. It's just because of inexperience in the matchup tbh. People just need to play more matchups with people who know what they're doing.
Samus has amazing answers to platform camping. She can get a full charge shot, then she goes to a side platform and shoots homing missiles until the opponent has to eventually land on one or vacate the top platform. She doesn't have to commit very hard against campers because missile damage is pretty considerable and the charge missiles can knock the opponent offstage to setup for her finishers.