It all depends what floats your boat. Demoscene is not easily generalised, there are many different disciplines of coding.
If you are going to write anything less than 4KB you obviously need to ditch Blitz, code a softsynth for your sound and use shaders. These days a lot of tiny demos use raymarching like muon baryon in the clips above.
If you're going to use Blitz I don't think that anyone would hold the file size against you.
If you want to win a comp somewhere though and your demo is 20mb + then it needs to have great content. I remember someone did a nice demo with Blitz 3D with a dancing robot.. I can't remember the name of the demo but it was quite good

I think that programing language fanboys exist only in their respective communities, most of the demoscene is 35+ years old and are old enough to have seen the times changing and appreciate a good demo no matter what language it's been made with.
Even people who use demo tools like werkzeug can get good kudos if they make something cool!