If it is an older macbook you can get to the drive and throw it in an external enclosure and access it. If it's one of the newer ones (especially 2018 forward) I don't believe you can get access that way. There's a new security chip related to the touch ID system that encrypts everything. I believe I've seen you can't get to those. Perhaps a specialty shop might be able to unsolder the chips and access them, but I wouldn't count on it.
OSX has a really nice feature called TimeMachine. If you have an external drive you plug it into every now and then it can backup your whole drive and you can reload from it. Without a backup you may be out of luck here. I'd probably try sending it into apple before giving up on all hope.