I'm sure you're aware, but if not, Fastmail trains a spam filter based on your email[0], and after you train it, it -does- get better. It just takes time. I haven't had my address for as long as you (only 15 years or so), but I have been just as nonchalant about sharing it openly. I get plenty of spam, but it's all sorted automatically now, and I don't miss Gmail.

[0]: https://www.fastmail.help/hc/en-us/articles/1500000278142