Acting like Amstel and Fleche are some mickey mouse races is quite disrespectful I think. I don't really know what I'd want, I consider the other Ardennes races some of the biggest one day races outside the monuments and having all three of them counts for a lot to me. Especially if you can pull off the mythical triple, and thats not that unrealistic. I think even Red Rick wouldn't state something like "Monuments is all that matters". And Amstel maybe is the 6th biggest one day races after the monuments?
Right now, we don't really have the big Ardennes specialists and the crosser don't race them, but in some eras these races are extremely contested and hard to win. That might be different this year.. but look at Gilbert, some of the first you think about is him dominating Cauberg (also due to his WC win ofc) and Valverde, you think about him dominating Mur de Huy.
I don't think they're mickey mouse races, I would put Amstel up there with GW, probably slightly below Strade Bianche now. It's just different from the week that precedes it where you have 2 monuments in 8 days, and both these monuments tend to simply be more hyped than Liege.
Fleche and Liege are in a weird spot with the 3 best Ardennes riders also being 3 of the 4 best GC riders in the world. Amstel is in a weird spot cause it's not actually that well suited to the 2nd line of contenders for FW and Liege, so it kinda doesn't blend that well but whatever. I do like the change of route in AGR a lot.
To me the fact that Van Aert and Van der Poel are skipping Amstel are quite telling however that its status is quite a bit below the monuments. Yeah both have ticked it off their bucket list, but both prefer to rest instead of trying to win a 2nd one a week after absolutely dominating Paris-Roubaix.
But in a way I think these hypotheticals of "would you rather win x or y+z" are very disingenuous because I'm pretty sure any rider would absolutely love to win Amstel or Fleche, and you never get to make this weird choice of designing your own palmares like it's an RPG.