I remember back when reforging existed, one of the main philosophical arguments was that when a new upgrade item drops for you in raid (and now M+ included), that you should be able to basically instantly equip it and gain the instant gratification of that. It was given as the reason for reforging being removed despite removing hit and expertise in the same patch.
But crests and flightstones now violate that philosophy. Its sometimes fixed by having an upgrade person inside the raid (accessibility and proximity of their location per boss may vary). But unless you prefarm all of your crests for an entire week going into a raid, you physically can’t “just equip an item” (and maybe add quick enchants to it that you can keep in bags via scrolls). Now you have to go farm enough crests (optimistically a 30m time commitment for just a single upgrade step, meaning several HOURS per week in total) and/or flightstones.
Worst of all, you can’t prefarm your flightstones going into a week either. You can start the week at 2k, and thats not enough to cover upgrading say a 2h weapon along with 1-2 other pieces of gear during that week. And usually the flightstones per crest reward ratio means you actually end up MORE limited by flightstones on main, than crests. A Hero Track 2hander going from rank 1 to rank 6 takes 2,200 flightstones by itself.
and at the start of a season/week, its physically impossible to prefarm your crests in a place that doesnt drop upgrades. Even if you want to prefarm before raid, you’re doing that in M+ which will have numerous upgrades for you too, which make you do even more chores of M+ to be able to crest/flightstone upgrade them. It just adds significant time AFTER every item to gain the actual power benefit of it. Its the opposite of the old design philosophy of items and a notable step backwards in feeling of fun/satisfaction/joy when gearing.