Most RPGs have a problems with balancing what you can buy in shops with loots and drops and the overall amount of gold you get in the game. Unfortunately it's a zero sum game whether found items are or are not better than those you can just buy in a shop. In the one hand stuff in the shops is devalued and on trhe other loot and quest rewards are devalued.
One of the best balancing acts in IMO was Dragon Age origins. There you had a fairly large selection of uber-items around the shops sold for exhorbitant sums of gold. In general they were better and there where more of them than you could afford to buy with gold earned In normal gameplay, you had to choose between them, and you only got a few top quality items from looots or drops IIRC. You had to quest hard to make enough to get any of them, and you had to pay close attention to dialog options/quest solutions that might make you extra gold.
Then for some inexplicable reason they put in the Lyrium Potion exploit that allowed you to mint as much gold as you wanted easily. I guess it may be Bioware worried people would get upset not being able to buy all the good stuff, so felt they had to put in a back door to it.
Many games have made a mess of this. Witcher 3 for example. Outside of the first hours of the game there is nothing in the shops, except a few runes and Gwent cards perhaps, that you have any interest in at all. There is tons and tons of fancy gear to be bought, looted and found in the game but all you are intersted in is Witcher diagrams to craft Witcher gear, i.e. the best gear, which in the scheme of things in the game is cheap as chips to do. You have no interest in loot or shop inventories and no need of money for anything.
Another problem I believe bedevils this issue is that playing first time blind the whole question of gear looks very different to what it does on a second or third run (or if you make etensive use of Google to guide you shopping expeditions). I think it is reasonable to say it is best practice to design and balance quipment availablity for the first time blind playthrough having no idea what equipment is available where as you progress. However that almost necessarily means that the a player on their third run who bee-lines preferred specific items, as you do, will end up with a) a mountain of useless gold and b), overwhelming disappointment at the stuff offered in the shops.
A final issue which I think contributes to people who play a lot of a game feeling the equipment available to buy in the shops is distinctly lacklustre is the necessity of scaling the power curves of equipment and ultimately capping them at some point to balance end game challenges. Let's face it if a piece of equipment is not significantly more powerful than what you already it is by definition lacklustre.
Personally I think Pillars did a pretty amazing job on this front considering how hard it is to get right. There are a lot of exiting loots and drops to be earned. There are also a number of excellent items available in most shops. I typically use both over the course of a game. There is no one piece of equipment of any type that is demonstrably and indisputably better than all others of that type in the game but they do have very different attributees and charcteristics and suit different approaches. I still find myself mulling over whether I want to use this or that items for a character, and the decision is sometimes pretty tricky. Which to me is saying Pillars has done a pretty good job equipmewnt-wise on the whole.
The one thing I would say is I would like to see some sort of solution to the mid-to-end-game gold mountain problem. In the end the need to make a bit of coin is a good reason to get out of bed in the morning and go questing, and if there's nothing to spend it on, well, a bit of the magic is lost somehow. Yes, you can put in "gold sinks" (such as a few things that happen along the way at the Stronghold for example) but the fact is, and here I agree with the OP's general drift, this is not the same as unexpectedly finding a fanatastic weapon, suit of armour of ring to spend 100,000 of yopur hard earned on. Not the same thing at all.