I heavy disagree.
You're sitting there shielding
Why are you sitting in shield? At high levels, you're just going to quickly press shield to block an expected attack and then do something else, not make decisions while hiding within shield.
How much health your shield has
How much health your shield has is something you think about before you decide to shield, not during. Shield is a resource just like a second jump or Banjo's Wonderwing, so before you spend the resource, you do a quick mental check, do I have enough to spend? And then you either do it or you don't.
-What are your options
-What options the opponent has
-What their attacks will do to your shield
-Will they grab or do an option that beats shield
-Can you parry it
You're weighing many dozens of things simultaneously even when you're not shielding. For example, say you're dashing away from your opponent, you may think:
-how will my opponent follow my dash (dash in? jump? roll?)
-what will that mean for my spacing
-will they choose to attack or not
-will I have time to parry
-what percent am I at? do I want to put myself at the ledge or try to roll behind
-but wait. how much have I been rolling lately? will my opponent spot that
-Should I angle my shield
-Will I get shield poke
These should be considerations before you decide to shield. Ideally, when you choose to angle your shield up or down, it's in response to expecting a specific attack from the opponent, like a Pikachu aerial. So in most situations the decision is unambiguous--your opponent is in the air? Angle shield up, no reason to angle it down.
And if it's ambiguous? That means you're playing a grounded neutral, in which case you don't even need to be shielding since you have so many good universal options (dash back, tilt, walk, spotdodge, roll).
-Is my character prone to getting shield poked
Shouldn't you already know this well before the match even starts? Why is this something to focus on?
Shield angling solely exist to try countering shield poking as a mechanic, but it provides no other uses or help outside of that.
it's not much different from SDI in this regard; how do you feel about SDI?
High and Low systems work in other fighting games since often there's no limit to how you long you can keep your guard up. It's there to force the blocker to adapt and do something new.
In Smash, you're losing health just by keeping it up, you have to do something new or you're going to get grab/shield broken. That's a good enough to keep shields from being lame.
Shielding gives you instant invincibility to all non-grab moves, and with very minimal endlag, which is a
lot more powerful than blocking 50% of attacks. This extra power means that you don't have to think about it much--the limited amount of cognitive load that angling adds to the equation still doesn't make smash shielding as complicated as high/low blocking in other games.
If you're at low shield health, your punishment of shield break is enough to keep you from wanting to shield.
Not even being allow to shield weaker moves during this state without getting hit is just too much.
What, specifically, makes this "too much" in your eyes?
If shields had less health if it meant shield poking was gone forever, I'd take it with open arms.
Shouldn't the ideal solution be to buff those characters who are particularly susceptible to unnatural-looking neutral shield pokes, instead of eliminating a skill-testing mechanic entirely?