Why is uncharted 1 so hard?

I have already platinumed uncharted 2 and 3, left uncharted 1 for the end, in my plan to platinum the whole Nathan drake collection.
playing uncharted 1 on crushing and all the encounters are way too hard, enemies don't die easily, cover system is not that great, arenas are small and limiting. I don't know what to do lol