>destroy Bitcoin by maintaining a 51% attack

The 51% is a better chance attack, you can still try to perform it with 10% and succeed and you can try with 60% and fail.

>Bitcoin could easily be worth nothing in 10 years, it's a poor Store of value.

Gold is more and more used in electronics, less and less in jewellery, if we move to graphene-based computers gold will not have much place there and its value in USD will probably drop. One nuke on Hawaii or California will cause huge drop in value of USD compared to other currencies.