Let me compare an ISP spying vs a VPN spying:
1. You make DNS request about example.com. Your ISP sees this. Your ISP can see what websites you "might" visit.
2. You connect to 1.2.3.4. Your ISP sees this. Your ISP can see what websites you "did" visit.
3. You request some data and receive some data. Your ISP sees the size of the data. If it's not encrypted, it can also see the content. Your ISP can see (at least) the size of objects that you requested -- which is enough to fingerprint many specific contents.
Okay so not using a VPN gives effectively zero privacy. Let's look at a VPN:
1. You connect to a VPN (and let's assume your connection doesn't "leak" insomuch as now _all_ network traffic goes through the VPN). Your ISP can see this.
2. You make DNS request about example.com. Your VPN sees this and your ISP can see a network packet. Your VPN can see what websites you "might" visit, your ISP can't.
2. You connect to 1.2.3.4. Your VPN sees this. Your VPN can see what websites you "did" visit. Your ISP still sees traffic to the VPN.
3. You request some data and receive some data. Your VPN sees the size of the data, and your ISP only sees the aggregate-size of data across all of your sessions. If it's not encrypted, your VPN can also see the content but your ISP should still only see aggregate size. Your VPN can see (at least) the size of objects that you requested -- which is enough to fingerprint many specific contents. Your ISP will have a tough time fingerprinting content from specific websites.
4. Your ISP can note that you have a high amount of traffic, possibly note that the traffic is going to a known VPN destination, and that your "normal" traffic is now gone.
Now, your VPN can see all the stuff that your ISP used to see. In addition, your ISP can now determine that you might be doing something illegal, suspicious, or at the very least "enterprise grade" and demand more money.
Have you really gained more privacy?