Your customers are regular people. Talk to them like you talk to regular people.
Look at the simple, clear language in this Apple alert.
Here’s the action plan: Hire someone (permanent or freelance) to review everything you write. De-lawyer it, de-engineer it, de-jargon it. A few days of rewrites will completely change how your customers perceive you and relate to you.
Then create a style guide to prevent jargon from creeping back in (like this).