I came across this approach a while ago: https://uxdesign.cc/form-field-required-vs-optional-9b4d7cdbf400

Their solution was to only mark the optional fields which I prefer because it naturally implies that unmarked fields are required and cuts down on repetitive details.

It is probably important to consider the ratio of required to optional choices, because if a good portion of your form is optional, the noise level goes way up and you have the same issue. But that scenario suggests there are some bigger problems at play with the form.

When it comes to consumer forms, like account registration etc., I personally feel that optional questions should not be included. If you want users information then actively seek out users and engage with them or send out surveys to get them to offer their details. Optional fields are lazy, bothersome, and often marketing related.