You can be tracked via IP address online, but this by no means is the only form of tracking. It has been proven time and time again that this form of tracking is not really effective. A browser fingerprint is far more likely to be used.
This is true, but only in the browser.
If you for example joining a Minecraft server the IP is used for tracking.
Sure they can sell that data to Big Tech, but if you are already using something like Pihole or NextDNS combined with UBO, how much is their tracking actually effective at that point?
The first packets from the client and web server (Client Hello) are unencrypted. In their you have a few data sets like the domain. So even with strict HTTPS, TLS1.3 and DoH the ISP or Network Owner (pub. Wi-Fi) are able to say which website you visit.
In addition, the ISP also gets your SIM Id. (IMEI) and the approximate location for your device.
They are also able to make a user profile on when and how often you use the phone (how much traffic from your device goes when out).
It should be also mentioned that depending on your country your ISP is forced to have a data retention policy.
And please also be aware that if you live in the EU the GDPR doesn’t protect you much on the ISP site.
I would rate the EU ISP and the US ISP at the same level.