There's a third option and I use it to explain things to stupid, old, and Boomer people. Not that those are mutually exclusive but that's beside the point.

You have to dumb it down but still be concise. Use the fewest number of words necessary, and explain it in a way that any idiot can understand. For example, when I explain how computers work to my dad and stepmother, I explain it with simple analogies like "The hard drive is where the memory lives, the ram is where the short-term memory lives, the processor is where the thinking happens, and the motherboard is the body that holds it all together."

When writing manuals, as in for work procedures, You need to also give them step by step specific instructions, with pictures if possible, screenshots will do for software, so they know what to look for. I've worked with a lot of tech illiterate people and you really need to make it super simple so that everybody can understand that page 3 explains how to do this thing, and page 5 explains how to do the other thing. No preamble, no flowery language, just simple instructions, including literally which buttons to push in what order to make a thing happen. Also including a this is what you do if something you don't recognize or understand happens to go backward, and a reminder to ask for help if all else fails or you get confused.

I worked in a warehouse for 10 years and that exact procedure worked great for teaching people are stupid, goofy, proprietary, 30-year-old pre-Windows XP software, along with windows instructions for how to get it working where necessary. You might feel like you're talking down to people, so if it's verbal you have to say it in a non-aggressive, non-confrontational, helpful tone of voice, ask them if they understand, etc. If they ask why it seems so simplistic or see that you can skip a certain step because they understand it already, you just tell them that they have to make the manuals understandable by everybody, and that you have to explain it to them this way because you're made to by management. Always pass the blame uphill.