Exodus and Ezekiel are talking about two different Temples. The apparatus to the JPS Tanakh Jewish Study Bible 2nd Edition states:
The details of the Temple, its courts, furnishings, and laws and the
technical terminology presented here differ in many respects from
those for the wilderness Tabernacle (see esp. Exod. chs 25– 30; 35–
45), Solomon’s Temple (1 Kings chs 6– 7; 2 Chron. chs 3– 4), and the
Second Temple (m. Mid. 5). Indeed, the differences in the portrayal of
the Temple were, according to the Rabbis, a major discrepancy that
Hananiah son of Hezekiah reconciled so that Ezek. could be included in
the biblical canon (b. Shab. 13b). Because of the discrepancies, there
is a strand in Jewish tradition that regards these chs as Ezekiel’s
vision of the Third Temple to be built in future days (Seder ʿOlam
Rab. 26; Rashi; Radak).
Regarding Exodus 20:26 (v.23 in the Tanakh), the explanation is given:
The altar must either be low or, if built on a platform, have a ramp
rather than stairs to climb onto it, lest one’s private parts be
exposed beneath the skirtlike garments that were worn. According to
the Priestly legislation, in the Tabernacle the priests were required
to wear undergarments for this reason (28.42).
A Christological interpretation of Ezekiel would be that the Temple he is describing is not a physical Temple on earth, but rather a heavenly one (viz. Hebrews 12:22, Revelation 21:10). That being the case, perhaps the purpose of the original prohibition on steps would no longer be relevant.