What issues involving form accessibility are an issue? The forms don't have any major accessibility issues that I am aware of.

While tabindex can't be disabled from the admin tool, it can be disabled via an API hook by adding a line of PHP to your functions.php file. Most users want tabindex which is why it is on by default. Tabindex can be customized via an API hook to adjust the tabindex order or you can choose to turn it off completely.

Of course reCAPTCHA isn't required. It's just one of many field types. If you don't want to use reCAPTCHA, you don't have to use reCAPTCHA. None of the field are required. The forms are customizable so that only the fields you want to use appear on your form.