> In the 90s we also had tons of closed code on our computers
Sure, there was much closed code, but there was no signed or trusted code. You could still reverse engineer, patch and reflash every single bit of it to your liking, provided you knew what you were doing. On modern hardware, even dumping the decrypted binary for the "trusted execution environment" is a challenge, and getting the thing to run your modified version is simply impossible because it needs to be signed with a key you don't have.
Sure, there was much closed code, but there was no signed or trusted code. You could still reverse engineer, patch and reflash every single bit of it to your liking, provided you knew what you were doing. On modern hardware, even dumping the decrypted binary for the "trusted execution environment" is a challenge, and getting the thing to run your modified version is simply impossible because it needs to be signed with a key you don't have.