For many things, it's not just Covid restrictions, but also a matter of staffing up. Not every trained staff member is sitting by the phone waiting to be recalled to start the next day.
And the college program needs months of lead time.
Thus, many things can't come back until staffing is brought up. And this will be a process that takes weeks to months, depending on the particular item.
And with Disney cost cutting, they don't seem in any rush to staff back up. In theory, if they wanted to have a much higher level of operation by Memorial day, you'd start hearing rumblings now or soon. For example, if they anticipated having Fantasmic back by Memorial day, you'd be hearing about staff starting to get calls now.