i tried to download the downloader but cant open it. what are my options now?

Maybe this topic could help.
https://forums.d2jsp.org/topic.php?t=84635056&f=34

For me, I had to boot up a copy of windows on my MacBook Pro to get it to work properly. Diablo 2 just doesn’t work well with new Mac Operating Systems. Even once I had windows 10 on my Mac I still suffered crashes. The crashes happened enough that I just gave up playing. If you run something like windows 7 that may work better, but I can’t confirm it.

Diablo 2 won’t run on newer systems like Big Sur, only on El Capitan

As a 32-bit application, Diablo II will not run on MacOS 10.15 (Catalina) or later.

Boot camp with a copy of windows is your solution

virtual machine is something.

Try crossover you can run the d2 installers through that if you need halp send me a dm

Check this topic: https://forums.d2jsp.org/topic.php?t=71815420

Founded how to install, thanks guys!