Most of the minor events should definitely be simmable at this point - Fleet Mastery, Dathomir (especially if it means avoiding another invincible enemy bug), SR II, Endor, etc. The only exception I can understand is if the tier/event requires the "featured" GL. Like right now, the tiers in the Endor and UJ events that require Leia. But everything else, even SR II (considering Jabba hasn't been the featured GL for well over a year now), that should have a sim option. Just look at the DoF event, it's still relatively new, and even when it was first released it came with a sim button.
The major events, that's where I don't completely agree as being simmable. TBs, Raids, TWs, etc., the goal is for us to work, especially as a guild, to actually earn rewards. Still, I agree that a lot of them can be frustrating at time because of massive RNG and/or burnout because of their running concurrently. Here, it's better if we get, though I unfortunately doubt we will anytime soon, a schedule rework. TBs are great, but, especially if you're at a point where you only focus on RotE, they eventually get stale. Conquest is as a whole a good event, it's just the feats that make it a grind, albeit to a lesser extent these last few seasons. The Naboo, or any for that matter, raid puts you against unique enemies with unique mechanics, but these latest raids are insanely filled with RNG that you have to do several attempts with just one team. Put them all together, you're heading quickly toward burnout. Make it so that TBs and TWs run for only a week each instead of two (with double rewards of course). Example, have the first week of the month be for TBs, the second and third for Conquest, and the final for TWs, or anything like that. GAC and Raids can stay unchanged. With a rework, the events will again have a bit more excitement in them instead of quickly becoming stale, the game will (likely) once again feel like a game instead of a chore, and there will be a lot less chance of burnout and/or quitting.