The most dangerous thing about email is that it can send you to a malicious website. The troublesome thing is that you can’t (in general) choose who sends you emails. Ads are similar, you may choose to visit a site that you trust, but you don’t choose the ads that are served by that site to you and these ads can be malicious. The site owners that you trust may not even know the ads that are being served to their visitors.
Any reasonable email reader will allow you to turn off HTML, execution of Javascript, and any resolution of outside URLs. That render email pretty safe. It's how I've been doing email for decades.
Yes, plaintext email is awesome! Too bad most major providers hide the option (or straight-up don't have it).
I'll just plug https://useplaintext.email as a great resource. The main recommendations are... opinionated (this site is run by Drew Devault, after all), but the instructions are very useful. I personally use thunderbird.
