There are 2 small issues here.

1st is whether you actually have ALC1200 or ALC1220 as there is a big difference between them. ALC1200 is capable of only 1V 30mW at 32Ohm, while ALC1220 is capable of 2V (don't know the power).

2nd is the MSI implementation of it. My MSI Z690-A has only 3.2mW out of ALC897 (a $229 board with low end chip...) and it has 80Ohm output impedance at that. I don't know how powerful the ALC897 can get, but certainly that board is much quieter than than my other Gigabyte board using ALC892 (the same chip, ALC897 is a refresh). I recall multiple posts of people at HeadphoneAdvice complaining on low output of their MSI onboards, at least 2 of MAG Mortart series on B series AMD chipsets.

That said DT770 are an entry level closed backs and you simply might not like their sound.