I always hated this argument. It feels to me like someone is complaining why a train can't go from 0-60 in 10 seconds while many cars can. The answer is always "because that's not what it's designed to do".

Regardless of how you feel about it, the team behind Atom made a design decision to sacrifice performance to gain a large amount of other benefits ("easier" higher level language, easy cross platform support, extremely easy to write plugins for it from it's target "demographic", etc...).

Because of those architecture choices, things like spawning a new window aren't as easy and straightforward as they might be in another architecture.

So just because you want a method of transportation that goes from 0-60 in 10 seconds, doesn't mean that all methods of transportation need to go from 0-60 in 10 seconds. And just because a method of transportation can't go from 0-60 in 10 seconds doesn't mean the designers were lazy or cut corners, it just means that they prioritised other things, and are solving different problems.