There's a balance between the two and that balance shifts based on product/project requirements. I can't imagine anyone writing a slow browser engine and being like "yea but we will make it fast later!", Screen tearing, 5second plain text page loads, etc don't make for compelling demos. Similarly for an OS or a database you can't have it be below some reasonable performance threshold even in prototyping. Otherwise you aren't even solving the problems, the apparent remaining 10% of the work basically demands a complete rewrite plus many new feature editions - ie youve done nothing.
> I can't imagine anyone writing a slow browser engine and being like "yea but we will make it fast later!"
Funny, that’s the exact opinion of the people building Ladybird for SerenityOS. They are of course doing it for fun, and it doesn’t take five seconds to show text.
