If there is more gold, it’s value should go down. The price should only go up when supply becomes limited, or some new thing demands more than usual.

You're thinking of Gold as a consumer good, I'm thinking of Gold as a currency which is what traditionally gold has been. Even nowadays very little gold is actually consumed (it's used in small quantities for things like wiring inside a microchip package the pads of the dies to the package pins).

When a cross-currency exchange rate changes all that you know for sure is that the relative value of a currency has changed vs that of a different currency - maybe one currency went up in worth, maybe the other currency went down in worth, maybe both at the same time, maybe both went down at different speeds, maybe both went up at different speeds.

It's exactly because "if there is more gold, it’s value should go down" AND gold has being up in quantity by about 1.2% per year due to mining, that I'm saying that the movement of the cross-currency exchange rate of the GLDUSD pair is more easilly explained by the fall in value of the US Dollar rather than by some greater worth of Gold.

It makes sense that the currency that nowadays is mainly created when banks lend money (as explained in the Bank Of England paper "Money Creation in the Modern Economy") would lose value way faster than the currency that's created when more of it is mined and mining only adds around 1.2% to its amount in human hands per year.

I'm actually saying that Gold is going down in value, it's just that the Dollar, Euro and most other paper currencies are going down in value even faster so the cross-currency exchange rates between Gold and those currencies are such that the same amount of Gold can buy more of those currencies.

Gold has a lot of practical use, but because it’s value is hyper inflated it is almost always more cost effective to use a cheaper material.

Well, you see, you got the consequence right but you didn't go back enough enough in analysing the causal chain to get to the root causes - gold price vs the price of inferior alternatives for many of its uses, such as Copper, is at its root what it is because there is way less Gold in the Earth's crust that we can mine than there is Copper as you can see here (note that the vertical scale is logarithmic).

Copper is between 100,000 and a million times more abundant than Gold.

Per your logic Gold should be at least 100,000x more expensive than Copper, not just 10,000x.

In Human History stuff that is rare and doesn't decay tends to become a store of value - at one point even Aluminum was a store of value because it was rare since the process to extract it from Bauxite handn't been invented yet.

This also means that if suddenly some way to mine way more Gold is found (say, asteroid mining), its price will collapse vs things that don't benefit from it, similarly to what happened to Aluminum when the process to get it from Bauxite was invented.

It's the modern government issued currencies whose tokens are not themselves rare materials (the so-called "paper currencies") or a stated guaranteed IOU for a rare material (such the USD was during the Gold standard when the USD was legally tradable for Gold by the US Government at a fixed rate) that are in Historical terms unusual and very recent (less than a century old). For me it makes sense that any weird movements in the exchange rate between Gold and government issued currencies is more likely explained by issues with these "recent" inventions rather than issues with what was a currency for millenia.