There is nothing wrong with using legacy form fields; the problem comes when you try to use them with Content Controls. These do not play nicely together.

That means no Date Picker. You can use a text form field and format it as a date.

In a Content Control form with restricted editing you can set it to show the next place the user can enter text with a different color. You can also get rid of the placeholder text in Content Controls.

You can also do calculations with content controls.