I play characters with this issue; you don't get great option coverage. This is why Lucina is so good; her attacks are huge arcs.
This is wrong.
There's nothing fundamentally strong about arcing hitboxes. This is obviously true if you think about Shulk from Smash 4--huge arcs, but poor performance. If anything, arcing hitboxes tend to be weaker than most others, because they take longer to finish the animation, and thus they're easier to whiff punish. What makes Lucina good is her disjoint and range; she could do without the arcs and be just as good (maybe better).
When Lucina is swinging f-air, depending on where I am in relation to her, she's often missed me completely
and is still swinging, meaning that she's locked into the f-air animation and I can hit her. It's almost as bad as being in freefall--almost because you still cover some of the space around you with a hitbox, but all this does is limit the range of punishes that can be issued.
Arcing hitboxes
do cover more options, but only if you're just swinging wildly, hoping to catch your opponent in a range of positions. It's a low- and mid-level safety net, but at the high and top levels, precision hitboxes (such as ZSS') aren't any worse than arcs, and in fact average a better hitrate.
Joker doesn't have bad hitboxes; in fact, I would argue that they are his strongest asset. His grabs, gun mixups, whatever else tend to be overrated, but he's super hard to hit when he's attacking, and that's what matters for his archetype.
I pointed out the flaws of RG and you moved the goal posts to "he can do this instead". Yeah a great way to not be punished for using a counter is to not use it.
What he means is that down-guns and rebel's guard
combined cover a lot of options--Rebel's Guard has 33f endlag, but you don't
actually have 33f to punish because you have to position yourself in such a way that you can also deal with the downward guns option. This adds ~8-14 frames of time for you to get into position.
You keep arguing with folks, misinterpreting their points, and acting condescending in response. Every time anyone responds to you and doesn't agree with your position you explode and say that you're done with the argument. Why are you reading so much into people's disagreements? I know that you have me on Ignore so you'll never see this, but I'll say it anyway just in case: please man, try to relax--you'll enjoy your personal life more that way too.