Code can be well designed from an architectural perspective and still be slow in areas. I imagine it's due to the minimal feature set (which MS defined). Stuff constantly happening in the background when you click or type something, bottlenecks become more apparent with really large projects and they just haven't dedicated time to improving that, etc.

I realize that architecture can't be separated from functionality, but I think the parent was focused on modularity and the ability to reuse various components.

...and still 32bit in a 64 bit world

There are valid reasons for that [0]. Would you accept slower compile times and more memory usage just so you could have a 64-bit version of visual studio that your project probably wouldn't even need?

0: https://blogs.msdn.microsoft.com/ricom/2009/06/10/visual-stu...

That was 8 years ago. Surely things have changed...!

Physics haven't changed. If you double the size of all your pointers, you effectively reduce the available CPU cache. It will be slower.

I'm guessing you haven't tried Xcode or Eclipse.