I entirely agree that you should have your own website. As Treyton says, you should own your content.
Even as I’m now on Mastodon and Twitter implodes, I’m not sure that I should be posting to Mastodon first. I should be posting here first and then sharing the content to other spots. My site should be the primary place to share any thought I have and if it’s not “big” enough for a blog post, maybe no one cares and I need to keep it to myself.