You need to be a YouTube Music premium subscriber for true offline playback.

I mean I copied the link of the music, used a youtube downloader and listen to it that way. The Youtube music App is broken AF.

There are two different ownerships that are being conflated here. When you buy a book, let’s say it’s a new book, just released, and rapidly becoming a best seller. You own your copy of the book, you can read it, you can make notes in it, you can lend it to a friend but while your friend has the book you can’t read that book yourself, or you can sell the book again but once you sell it you won’t be able to read it anymore until you purchase another copy or go to the library. What you’re not allowed to do just because you have the book is make copies of it to sell or give away (which is somewhat challenging to do anyway with a physical book that has hundreds of pages), you’re not allowed to make and sell an audiobook recording of the book, you’re not allowed to go and make a movie based on the book. You’re not allowed to take the characters and write a sequel to the book and sell it. The author still owns the rights to the contents of the book.

In the early days of books, especially the 19th century as books became easier to produce and more people could read, a lot of this started to become problems. People with printing presses would see a book people like, get a copy, and start printing and selling copies on their own. They made translations and sold copies in other countries. People would produce plays based on the books, and depending on where it was performed the author might never know about it. This was all usually done without the involvement of the author and the author often was not paid from these. A surprising number of highly regarded and top selling authors wound up making very little money from their books because they weren’t being paid for most of the copies being sold. Many died poor. This led to the development of the concept of copyright and various other associated rights.

These rights became more complicated as media progressed. With audio recordings there are multiple rights involved: the person who wrote the song has a copyright on the actual music and lyrics, and the person who performed the song has a copyright to the recording of their performance. Sometimes these are the same person, sometimes they’re different.

The laws kept getting more complicated. With software, the developer or publisher owned the software, often because the developer was working under contract to the publisher or sold the software to the publisher. It’s kind of rare to sell the actual software to a customer, and is usually done only for corporate or government clients. In that case the entire rights to the software are transferred and the publisher/developer can’t sell another copy to someone else. Much more commonly only a license to the software is sold to many different customers, and what exactly that license involves can vary widely in the legal terms of that license (which most people never read). Some are very restrictive. It used to be that a lot of licenses specifically tied the copy that you purchased to the hardware you first installed it on. If that hardware died or you purchased a new model, too bad, you’re now supposed to buy a new copy. Some licenses said you’re not allowed to change the code of the software, some licenses allow it. Ten or fifteen years ago people didn’t really think about the idea of streaming gameplay and creating a video from a game was considered a derivative work and not allowed, like making a movie from a book. Now a lot of licenses explicitly allow streaming gameplay, but some older games that weren’t planning for it might not have the rights to stream the music from the game.

If you violated those rights in the past, the terms technically said those rights ended and you were supposed to stop using the license. In practice this was on the honor system and the licensor would rarely know about it, unless they sent an auditor to check compliance, which was usually only worth doing at large companies. With the internet, companies now have the ability to actually access your computer and monitor your use of the software you’ve licensed. They can even disable your access to this software. Unfortunately, of course, a lot of companies have gone the greedy route and used this to their own advantage and at cost to the customer. Not everyone does, though. It’s really important to know what the terms of the license say. If they say they can delete the game you’ve bought and not refund you, don’t buy from them. Don’t give them money for this crap. Let the game flop, even if it otherwise looked great. Support the developers and publishers who want to support the customers. Read the terms on your software; you should always have the option to say you don’t agree and get your money back if you don’t go through with installation. And the laws that allow bad licenses don’t have to stay as they are; some jurisdictions are friendlier to consumers than others.

It’s the same with paper books though. If you buy a paper book you don’t automatically own the rights of that work. You own the copy and can sell that copy or even make a copy for private use. But you can’t make copies of that book to sell, since you don’t own the copyright

Copyright is definitely being abused by the big corporations but without copyright small artists/software developers would constantly get their work stolen by those big corporations.