Simply put: Don't write for chrome, write w3c conform.
Or better: Use standards which match most browsers at caniuse.com
Or better: Use standards which match most browsers at caniuse.com
At the moment some people develop only for Chrome because it has the most market share. So they deploy their site using the <toast> thing and suddenly people using Firefox are wondering why things are broken. At this point Firefox can either implement the new feature(s) or lose users. And once FF etc. have implemented it suddenly it's on caniuse.com as "works in all modern browsers".
which is probably why OP is suggesting it