Agreed, though Russian paranoia is a fact of life and we do have to consider that when admitting new members. Right or wrong, Russia may feel NATO membership for Ukraine is just a bridge too far. Call it national pride, or considering Ukraine its national buffer, or whatever, any Russian government may recoil at this. Still, your point is spot on. A free Ukraine should be able to petition to join whatever organization it wants.
To me the lesson is this: Don't give up your nukes. Never, ever, give up your nukes. If Ukraine had them today, things would be a whole lot different. At minimum, the Ukraine could use them as leverage to get a lot more Western help just by hinting they might use them to defend their territory.