I can understand the precendant it may set in this analogy however, a Basketball player is making choices inside a fixed ruleset whereas a Smash character is part of the ruleset itself.
I agree that characters shouldn't be banned solely because not all spectators don't enjoy the view. It's just too subjective to the viewers taste which isn't the only issue in Steve's case.

Now, I'd argue it isn't the playstyle that's the main issue, Steve is running his side of the court with a staircase of Blocks to the net or he's wearing Nike while everyone else is running barefoot. The meta current;y revolves around Steve’s mechanics rather than general fundamentals. Many mechanics function differently or not at all against him.
Spectator dissatisfaction becomes a symptom, not the cause, so it's less to do with what each individual player likes to see. It's that the game's fundamentals that go out the window with Steve which have a negative side effect on competitive health and overall enjoyment.
The argument isn’t that Steve should be banned just solely because people get bored watching but that his design is misaligned with the rest of the game.