I'm not an expert either. I'm a computer scientist, not a physicist. But the math behind QM -- at least the parts that matter for this discussion -- is pretty straightforward linear algebra. Really, anyone can learn it. So don't take my word for it, look into it and decide for yourself. You can start here:

https://www.amazon.com/Philosophy-Physics-Princeton-Foundati...

https://www.amazon.com/Quantum-Mechanics-Experience-David-Al...

Or, if you don't feel like buying a book:

https://flownet.com/ron/QM.pdf

Or, if you prefer a video:

https://www.youtube.com/watch?v=dEaecUuEqfc

BTW, it may come as a surprise to learn that I am actually not a big proponent of many-worlds despite recognizing that it is in fact a logical consequence of the math. If so, you may find this interesting too:

https://blog.rongarret.info/2009/04/on-shadow-photons-and-re...

and a follow-up written ten years later:

https://blog.rongarret.info/2019/07/the-trouble-with-many-wo...

>QM is pretty straightforward linear algebra

The chasm between my grades in linear algebra and my grades in quantum begs to differ... :(

There are two different ways of approaching QM: the physicist's way and the computer scienctist's way. You were probably taught it the physicist's way, which is not wrong, but obscures the parts you need to know to understand the MWI. That part really is pretty simple. You should try again.