@AgentSmith the reason for Frege to follow Kant was because most everyone had Anselm's ontological argument in the back of their heads when evaluating these matters, but most everyone also understood and appreciated Kant's rejoinder to Anselm (and Descartes, incidentally).

Sometimes you'll see a misinformed analyst claim that necessary existence is "obviously" a substantive property, but Kant would not have that, his major enterprise in the first Critique is a theory of modality where necessity and possibility are also non-properties.

Now, per Meinongianism, among other things, a separation of the concept of existence from quantification often occurs, but that just means that we can say that God exists without quantifying over God, which removes much of the bite from the intended arguments.

Indeed, we would often think that we ought not try to define a concept such that it analytically would have a certain number of instantiations. And so this is still where ontological arguments would seem to go wrong.

We would try to say, with Anselm, that the concept of God is of a being such that Its concept necessarily has one instance, but this seems presumptive, and anyway we would then be able to define semi-Gods such that there were necessarily two instances of the concept, then semi-semi-Gods with three instances of the concept, etc.

And generally, we would (without Anselm) wish to count the number of a thing by counting it in perception, or at least perception-like epistemic space, rather than counting it conceptually, since given the tight connection between conceptual and logical space, we would prefer to leave questions of what exists unsettled by "mere" logic.

In other words/"in conclusion" (hardly!), that something exists should be inferred dependent on other existences that "lead to" it, but God as an independent being is not supposed to be given from the creation, but unto this, so one wonders howso we should ever infer the divine aseity from something else.

(This is, incidentally, why divine simplicity often "rubs me the wrong way," since the standard reasoning is that if God isn't absolutely simple in every relevant way, then God wouldn't be a se, which sounds like a deduction of aseity from an axiom of simplicity, which deduction is then neither itself simple enough nor a good expression of aseity!)

OTOH we might believe that there are exceptions to almost every rule, including the, "No analytical existence claims," rule, and it might be thought fitting to hold that God is such an exception, here. So the part of me that is tempted by ontological argumentation gravitates towards such a possibility, too.

Now some theologians proclaim God as beyond our common notion of existence-and-nonexistence, i.e. God hyperexists if anything as such, or for God there is no difference between Its existing and not existing, on account of Its superlative essence, which is an even more enticing proposal, although also one such as annihilates the meaningfulness of atheism (which might tell against such a proposal).