First of all, katz was BIG because they had actual visitors coming to download different things. New DDL owners are just asking forum owners to submit their file, but why would they? Because you do not have anyone coming to your website.
From what i've seen;

More indexed pages on Google = Higher traffic (thats not totally accurate, but it usually gives you an idea how long the site has been around for + I dont really want to explain anything else).

Lots of DDL's dont have much content, except I believe Phazeddl + nexus? Maby mecho also, but anyways, imo people should stick to the larger DDL's. Its the reason why katz was an empire - soo many people submitted to it, so that they had much more quality content (for the most part).


Tl;dr - Dont bother with the lil guys