I'm not sure what you mean but I'll list a few statements.
Funny thing is, some old cleaners clean better than the newer chinese 12 amp vacuums that people buy and toss 2 years later.
The process of manufacturing something is always dirty. Be it batteries or the process of getting raw material for producing electric generator windmills.
Older machines usually use a lot less amps to run, so they're actually greener to use. Also using an old vacuum keeps it from ending up in the landfill.
The last thing and probably what you're referring to is the use of a shake out bag. Those are indeed kind of dirty, since some dust gets thrown back into the air. Though this is very minor considering if the user empties it out after each use. (As per some shake out bag machines recommend you do so)
Using a paper bag does help keep the dust level down, not to mention makes it easier to clean out the bag. As for the allergic type, one can use a HEPA bag which keeps more dust and junk out.
But in reality an old machine isn't THAT dirty. Modern bagless vacuums still unleash a dust cloud into the air whenever its emptied into a trash can.
Some newer "clean air" vacs have a butt ton of filters to replace, which isn't fun doing so considering that they're chock full of dust and other contaminates. Not to mention, tossing out these filters creates more unnecessary waste compared to simply tossing out a paper bag into the trash.
That's just my opinion on it really. Others are more than welcome to think otherwise.
-Alex