This is an interesting question! First let’s look at the verse:
Ex. 20:26 - “Thou shalt not go up by steps unto My altar, lest thy nakedness be discovered.”
Well, obviously a guy wearing a robe or a tunic with no underwear is going to show off everything he owns if he goes up steps that go over people’s heads.
But the basic priestly outfit was a long tunic all the way down to the feet with linen breeches underneath (covering everything from the kidneys down to the thighs), so unless they were worried about knees or feet, they probably weren’t worried about the priests literally exposing everything they owned. (Unless it was a place with super-high steps, like a ziggurat.) The earliest Christian churches were designed more after a secular Roman “basilica,” the place where emperors and officials held court cases and made announcements. The altar was placed up where the official would sit, so that everybody would be clear that Christ was in charge.
However, one of the most popular kinds of pagan altars in the Mideast was an altar “on the high places,” and these were often associated with fertility rituals (like Baalpeor). A lot of times people would make an artificial “high place” like a ziggurat in Babylon. So if you couldn’t have steps up to an altar, you couldn’t be worshipping that way.
But also, Moses’ altar was small and portable. The altar at Solomon’s Temple was a lot bigger. There’s a fair amount of evidence that seems to indicate that Solomon’s Temple and the Temple in Ezekiel’s time had steps going up to their altar, although some argue that it was ramps. But Ezekiel 43:17 says, “And its steps turned toward the east.”
At any rate, the way we construct altars and churches is not much like the way Moses made the tabernacle tent and the altar, or the way Solomon and Herod did theirs. We don’t use unhewn rocks or dirt mounds for our altars, either. We have a lot of freedom to construct things, and our altar steps don’t look anything like a ziggurat or a pagan altar with steps up to it. (Ours usually don’t go up to the altar, technically, but rather to the platform upon which the altar sits. Common Catholic usage calls that the altar too, but it’s not quite the same.)
Our priests also have a lot less shallow steps to deal with, they usually wear stuff underneath, and there’s no chance of them exposing themselves to us just by lifting their knees really high to climb.
The Christian tradition for altar steps is that they should have an odd number. Three steps for the Trinity is usual.