Am I understanding Delta....?

Here, the Greek letter Delta (Δ) is being used to denote "difference" in the same manner it is used in some sciences and mathematics.  It is not an upgrade like omegas, zetas, or omicrons (also Greek letters). It simply means the difference between an attacker's and defender's relic levels.

You are not buying anything new to bypass relic levels; it is meant to make the (high) relic levels you invested in more worthwhile. You presumably might have more incentive now to buy those relic levels which already existed.

You might be getting confused because they said new characters will skip relics and gear--we won't know what they mean by this until it is released, but my guess is new marquees will come with lightspeed tokens. But this is to free up relic resources for older characters, as relics will be more important than ever.