Solemn First Confession is an excellent practice that underlines the importance and purpose of this Holy Mystery. If it arose from Latin influence, so what?
Because it did not grow up organically in the Church under the guidance of Holy Tradition but rather comes from a schismatic outside source and does not truly reflect an Orthodox "worldview", that's what.
Where do we begin to undo the "damage?" For instance, the EP got jurisdiction over Greece, Albania, Serbia, Bulgaria to grant autocephaly to them from the Iconoclast emperors detatching Illyrium from the jurisdiction of Rome (in punishment for the iconophile status of Rome) to that of Constantinople. That would call into question all those autocephalous local Churches.
All those pagan practices baptized by the Church (like the Pentarchy) grow up organically in the Church, under the guidance of Holy Tradition?
Whatever is true, whatever is honorable, whatever is right, whatever is pure, whatever is lovely, whatever is of good repute, if there is any excellence and if anything worthy of praise, dwell on these things. Phillippinans 4:8. Hence why many Orthodox prefer the King James version, which is from a heretical outside source.
At the very least, this is the argument that can be legitimately put forth. Also, we Orthodox are loathe to nail things down and define them unless absolutely necessary, and your argument has the effect of making me veer more towards the idea that any latinisation is bad, no matter how residual. The very phrase itself, "solemn first confession" sets off alarm bells for me.
LOL. I used it only because you OP did. I just say "First Confession."
It represents a very particular view of the nature of this mystery that I fear is grounded in a Roman Catholic understanding of the sacrament.
Which is differs from the Orthodox one how? (age of reason, etc. being necessary to confess, etc., necessity thereafter to confess for communion etc.)