The mindset around here is "everyone should design things for my extremely specific use case that 99% of users don't share". Find me stats about the % of users with desktop browser windows narrower than 900px and then we can talk.

What is "important" in this context? Resources and About? Do you just hide stuff under "More" from right to left as you run out of space? How many people are actually going to click or hover on "More" to find out what's under there? There's a reason design trends have been shifting toward hamburger menus for smaller layouts - it's the best design choice for usability and lack of confusion once people get used to what the hamburger icon means.