What is your definition of successful? Even good designers output work that doesn't hit the metrics they were after (which is the reason lots of companies go with agile development. You don't get things right the first try). Another definition could be monetary success, but even then a good designer taking a low paid job at a new startup or non-profit/charity would be paid less than a worse designer, so this isn't a measure of success.

"you're gonna need to communicate effectively with clients, stakeholders, co-workers."

Maybe at an agency, but a designer in a product team or self employed on their own product doesn't need to be good at that, or even do any of that to be "successful". And the best teams are made up of people from all types.

I have learning difficulties and other development issues. I'm bad with people and communicating, I've learnt some skills to get by that involve me communicating less than others. I'm literally telling people they don't need to be good at communicating to be a designer. But you and other commenters are belittling this notion and showing a level of distain for others if they are bad at communicating. Be it for social issues or disabilities. You really want to tell someone they won't be successful as a designer if they have learning difficulties? I would prefer if we could understand that not everyone is the same and some of us need to work around in other ways to get the job done. And getting the job done is my definition of success.

So if anyone else out here is trying to be a designer and are bad at communicating don't listen to these commenters.

I've worked with with UX researchers who do the communicating with users, PMs and business people who deal with clients. And there are other systems you can put in place to help you. You can be a good designer even if you are mute. Design is understanding a problem and using design thinking to achieve a goal. Do that and get paid then you are successful.