I think 2021 is worse for the following reasons.

2020 is bad because there's no week to week revenue, but the clubs are still getting the vast majority of their sponsorship and membership support as they don't seem to be refunding anything like that properly (amazing really when you consider we are almost all getting literally stuff all for our investments minus a good feeling and a velcro cap).

But 2021 is a different beast.
-Any club sponsors contracts running out at the end of 2020 will almost certainly not be renewed, and if they are probably at vastly lower sums.
-It's going to be a nightmare to find companies with enough marketing budget to replace the lapsed and reduced sponsors, and even the replacements will be giving much much less.
-It's going to be harder than ever to secure government and/or AFL funding for any projects because so much money has already been invested in more important things that helping out professional sporting clubs with what are basically vanity projects is not a priority at all.
-Convincing members that renewing their membership at the same level is going to be very difficult. A family of four that have 17 game memberships and social club upgrades are going to be annoyed if you ask for anything near full value after getting almost literally stuff all back in 2020. They are a very good chance to severely downgrade their memberships.
-Any members you have gradually managed to upsell over the course of say 5 seasons (3 game member into 11 game member into 11 game reserved seat member into 17 game reserved seat member into 17 game reserved seat member and social club upgrade etc) almost definitely resets back a few levels meaning you have years ahead of you to try to get them back to the same level of financial commitment
-Members will be more wary of putting money down too considering their 2020 memberships were financial write offs and 2021 is no guarantee to be unaffected.
-Much harder to convince the mid level partners to do so again (player sponsors kind of level where they basically donate a not unsubstantial amount. It's going to be really hard to "sell" experiences and merch and the like).
-Big financial partners like Fox are going to be in big trouble and have difficulties funneling as much cash as they used to into the AFL system.

Basically it isn't as if we are back to normal at the end of this year. Many businesses and individuals will be recovering for years financially, and the AFL is cetainly in the "nice to have" category for most when prioritizing their expenditures and can expect to almost universally see roll backs in terms of how much money and support people are willing to give them if any at all.