Sure, you can write or run your own fediverse server that renders HTML-only page, and every time you see a Mastodon link you paste it in your server's lookup form and browse it from there. Honk (https://humungus.tedunangst.com/r/honk) is HTML only and very minimalistic. I'm sure there's frontends or clients for Mastodon that use less HTML as well, so you can also swap out Mastodon's default frontend for a less heavy one.