I cannot relate to what you are saying at all…
I play a ton and mostly open level 100 chests. I do all events, challenges, and PVP. I have 7 chests running nearly around the clock… almost exclusively Diamond chests with some Ruby sprinkled in and an occasional Gold if I’m trying to time things right.
I have no stock of weapon shards whatsoever and a slight stock of the others only because I’m saving them for the off chance of a Legendary. But, I have around 10-15 weapons, armor, and accessories each that I want to take up and they are still sitting at level 1. Sometimes it takes me 1-2 weeks to bank enough shards to get 1 item up to level 25 (weapons are the worst). Getting to 35 takes longer. Getting to 45, well, you have to get a legendary first. Armor seems to be the easiest to get for me. I can usually get a new item up to level 25 in just a couple days.
Is it possible that you banked all your shards at a time when shards were flowing better than they are now and now since you have so much high gear you just don’t need to spend shards often… and when you do, it doesn’t matter because you have a huge stockpile of them? I’m not sure if playing more helps or hurts the issue. I play a ton and open a ton of chests. This gives me more loot (possible shards) from chests, but it also gives me more weapons, armor, accessories, and spells that I then need to level. I have way, way, way more things to level than I have shards. It’s not even close.