Hello, bubuds.
Welcome to the Microsoft community.
I understand that you want to disable copilot in Microsoft Office applications after trying it and feeling that it affects word loading speed. Copilot is a new feature which is designed to provide users with smarter and more personalized assistive functions through Artificial Intelligence technology that provides users with smarter, more personalized assistance functions that increase productivity and creativity. However, if you don't need this feature after trying it out and still want to disable copilot you can do so by following the instructions below:

By following the steps above you can complete the disable copilot operation.Feel free to share updates with me on how things are progressing after you've completed the aforementioned steps. Should you have any questions or require clarification, do not hesitate to reach out to me. I‘d like to do my utmost to assist you.
Best Regards,
Hannah.Z- MSFT |Microsoft Community Support Specialist
Dear Hannah,
Your advice is wrong and/or outdated. No such option appears where you say it does.
Also, the alternative advice to turn off Connected Experiences also not help. In Excel, the Copilot UI features remain, the only difference is that they now pop up the advice to turn Connected Experiences back on.
For all others: There may be some light on the horizon. In Word, in Options, an actual option to turn off Copilot has been added. This does indeed disable Copilot functions, it seems. M$ claims that this option will be added to other Office apps over the course of February. I rooting for OneNote in particular, as Copilot is particularly overbearing there.