Toasts can be bad UX (usually when they are the sole feedback), but they are great in conjunction with other elements.
A confirmation toast with a page-redirection is a great way to add additional indication to the user that their submission was successful.
A warning or error toast in addition to standard form validation indicators gives a great secondary indication to the user that they need to change something.
And if implemented in a catch-all for nonspecified errors, it'll allow the user to preserve the state of their page vs rerouting to an error page.
If used as one tool in the toolbox vs the only tool in the toolbox, it's a great option.
A confirmation toast with a page-redirection is a great way to add additional indication to the user that their submission was successful.
A warning or error toast in addition to standard form validation indicators gives a great secondary indication to the user that they need to change something.
And if implemented in a catch-all for nonspecified errors, it'll allow the user to preserve the state of their page vs rerouting to an error page.
If used as one tool in the toolbox vs the only tool in the toolbox, it's a great option.