Life in the 21st century would be radically different without the internet. Its true nature of being a repository of information and a tool for communication makes possible many of the things that we take for granted.
This, however, does not mean that it is perfect. The way I see it, and yes this is pure opinion, It has these fundamental problems.
1. All connections should be encrypted all the time
Yes, a lot of our important communications are encrypted yet so much of our connections are unencrypted. While poeple in the middle might not know who and about what I have been chatting on WhatsApp, they might be able to infer enough from the fact that I have visited the website "Encrypting your connections". This shouldn't happen. Every connection should never give up the information that you have privately sent to someone else.
2. No one should know who you are communicating with
Short of using agents like Tor and Freenet, you can't protect yourself from letting outsiders know who you are communicating with. Sometimes the privacy we seek is not just in what information we are sharing but rather who we are sharing it with. Currently, while networks like that exist, we can't really make them our daily driver because they are simply too slow to use right now. If they are ever to become mainstream, these prbolems will have to be solved.
Of course, if these two pieces were to become part of the interent, you can be sure that criminals will florish in its ecosystem. However, the sad truth is that criminials already have better tools than this at their disposal so while yes, we make it more convinent for them to conduct their illegal business, much more importantly we enable the originary folk who wouldn't stand a chance otherwise.