If I want to still be able to look at the works of my favorite artists, photographers and animators, I will unfortunately have to use it to some extent. Some of them also post on other platforms like pixiv, which allows you to look at content without an account. If there is any other way to look at their content, I do, but some are Twitter exclusive unfortunately.
People will naturally follow their favorite artists and will want to interact with them. If you could somehow convince the creators to post on a free and open alternative, I would not have any problem completely deleting my Twitter account.
In the case of Reddit, I would delete my Reddit account if I knew that all the rock hounders, bug identifiers, mineral photographers and crochet enthusiasts were here.
So, what now? If you are able to, create content that people are interested in and post in exclusively on free and open alternatives. If you have any useful skills or know-how, help people on free and open alternatives with their questions and problems. That is how I got into Twitter and Reddit at least. Maybe it will work for others too.
And most importantly: be nice. Don't downvote people's comments and posts for no reason. Don't leave toxic comments. Say Thank you, give people compliments, provide constructive criticism and try to be helpful.