Unless your body is already dying, Death cannot take you without your consent.
All the times he tries to make Elisabeth come with him and she says “no”, he doesn’t try to force a Todeskuss on her. He leaves. She tells him “no” and he has to respect it. He can always come back later and try again, which he does, but when she tells him to get out, he gets out. That’s why he eventually sends Lucheni after her. Once she’s stabbed and her body is dying, Death is able to take her because she’s dying anyway.
We even see this with Rudolf–Death tries to kiss Rudolf several times during Die Schatten, but Rudolf keeps dodging the kiss. There’s no reason to believe Death isn’t strong enough to hold a human down and force a kiss on them. But Rudolf keeps refusing the kiss, and rather than force it on him, Death waits and tries again. During Mayerling, Death finally kisses Rudolf, but it’s with Rudolf’s consent. He’s killing himself–saying “yes” to Death.
I don’t know what higher power than Death is meant to exist in the musical-verse, but some higher power or cosmic law prevents Death from taking someone’s soul unless their body is already dying or they allow him to take them. If you say no, Death has to respect it.