In all seriousness, it’s long baffled me as to the position that the RCC and Orthodox take.
Generally, it’s the EO taking the hard line on the decrees of ecumenical councils.
Here, though, it’s Rome that is following the canon and the EO opposing it.
Nice didn’t say anything about the calendar, but rather set the universal observance of Pascha as the Sunday following the first full moon after the equinox.
At the time, this was a major calculation, so the astronomers at Alexandria (one of the five Holy Sees) were tasked to put tables together so that it could easily be calculated. If memory serves, it’s a 14 year cycle.
The problem is that the Julian/pagan calendar has room many leap years, as explained above, and drifts slowly–about 3/4 a day per century) out of alignment with reality. The days of equinox and solstice are the same nominal day each year; the day just, well, lands on the wrong day.
I think the solution is to dump the tables and use the actual equinox in Jerusalem; it’s trivial to calculate.