It SEEMS complicated, but I worked it out and it's not as bad as you think.
Clerics pretty much have 1 Reaction. AOO. Default is set to All Enemies, so unless you are an experienced player, you'll probably leave it as All Enemies. But the options I came up with are pretty simple and easy to manage even if you wanted to mess with them.
Druid is similar, but they might have Absorb Elements (Can't remember if that's in PHB or not. I don't have it in front of me.). That's also easy. Default is all element damage types. But you can easily go in and deactivate the types you don't want to trigger. Say you already have fire resistance. Deselect that from the trigger list.
Rogue. AOO. You don't get Uncanny Dodge until level 5, I believe, and even then. It's easy to manage. Default is All Enemies, but you can go in and set it to a specific damage amount.
