Fidelity Stocks and Shares ISA barely any investment options?

I opened a stocks and shares ISA through fidelity UK but there are very limited investment options – I can't even buy AMD or NVDA shares let alone much more niche stocks, am I being stupid? – why would fidelity restrict you from buying 90% of stocks.

I seem to be able to buy aapl and tsla but that's about all I've seen as far as individual companies go