With respect, this kind of argument needs to be further evaluated. Who set up the church in Bulgaria? The EP. Serbia? The EP. Romania? The EP.
So are you saying that the EP can tell all of these other canonical churches, "sorry, but we set up your church so we can take them back now"? That just doesn't make sense.
No, I'm not saying this at all. What EP is saying is that Kyiv was and remained a EP metropolis, given to Moscow to manage with certain conditions. A grant which the EP, seeing the pastoral need to address the schism, how the reasons for the grant are not valid anymore, and how the MP broke and continues to break the conditions of the grant, revoked in 2018. You know, the same logic EP used to give autocephaly to Church of Poland in 1940ies. Maybe this position can be disputed, but the thing is, Moscow is used to rely on the state to provide legitimacy, and it's own canonical position on this is not all that sound.
There IS a theory some in EP promote that yes, EP have the right to meddle in "new" autocephalous churches (starting with Moscow) should the need arises, because it granted their status and not the Councils. EP just didn't rely on this theory in Ukraine case.
Your argument about Moscow ignores the fact that the seat of the Russian Church was originally in Kiev, and that the Patriarch of Moscow is the successor to the Metropolitan of Kiev and All of Rus.
This is not a fact; this is an interpretation not all that faithful to historic realities, but flattering to the Empire. No wonder, because most rely on Karamzin tradition of Russian history for all that region, and it was explicitly written to cater to the Autocracy needs (not that unusual in national history). So, for example, people still casually mix up "Rus'" and "Russia" - this is a hint to the "Triune Russian Nation" notion that was the official dogma of the Tzarate (and assumed implicit dogma in USSR and under Putin Spycracy modern Russia). But deadly to Ukrainian nation.
Fact: Kyiv and Moscow were both EP Metropolises. Fact: Kyiv is a mother see for Moscow. Fact: some Moscow Metropolitans also had or claimed "Metropolitan of Kyiv" title. This is the totality of facts your claim relies upon. It is also a fact that when Moscow Tzars obtained Patriarchal status (and the implied autocephalous governance; 1589) for the See of Moscow, EP very explicitly excluded Kyiv and some other dioceses from new Patriarch's jurisdiction. MP intermittently installed a Kyiv Metropolitan anyway, but not by right; other times, there was an EP Exarch on the See (St. Petro Mohyla was one). Finally, in 1686 and following the Khmelytsky uprising that gave Ukraine to Moscow, Moscow bribed the Ottoman Court and Patriarch Dionisius do get a right to install Metropolitan of Kyiv (Dionisius was later deposed for simony, citing this exact episode). There was 2 conditions: Kyiv still to commemorate EP as it's spiritual head, and Moscow to respect Kyiv Metropolis's internal governance. As the Autocrat of Russia does no conditions once the document is signed, they were immediately ignored. And so it continued, until 2018.