One of the biggest issues now with "The System" is the changes in technology since it was written in the 1990s. He was writing when home phones were most dominant. Most people didn't even have basic cell phones then, let alone smartphones were text messaging was the primary communication medium.
@EyeBRollin has written about how someone can adapt the Doc Love principles with newer tech forms.
This is the hardest thing for old dudes like me (50 plus) to get used to. I am not comfortable with texting, on-line dating, or social media... so I just don't do it. I can get away with it since I'm older, so women excuse my reluctance, but you young guys have to master smart phone dating. To me it all looks like weak behavior... I know it isn't, it's just the way things are now. I am not knocking it... I just can't do it without coming off as ridiculous.
The only other thing I don't like about "The System", which is mostly pretty good is how Doc Love describes 'interest level'. In "the System' it is all about interest level. IMO that is over simplification, but there really isn't anything wrong with that but in reality... there is 'attraction' and 'interest'. "The Rational Male" IMO better describes what is going on. "The System" says a woman has to have 50% interest: "The Rational Male" says she has to be attracted to you.
I know why Doc Love does this because he's all about screening out women and he doesn't care why she gets screened out, only that it happens. But really attraction is a function of her perceived LMS you have. Interest is confidence, control, and challenge (CCC). LMS is internal: CCC is external. Doc Love assumes you are already the best version of yourself you can be (LMS), for many this isn't true. The System still works without self improvement, but the quality of woman you attract is not going to be as good as it could be if you don't work on LMS. The better looking, more money, and improved social status you have the more women will like you.