Co-authors either dismiss my ideas or don't understand them... and then dismiss them anyway
(1) This question could only be answered by reading your drafts and discussion carefully.
(2) If they invite you, politely decline.  (If there's more going on here, for example, a debt of gratitude, complex relationships with a third party, funding ramifications, etc., please explain.)
Now I'll pose and answer the question I thought you were leading up to.
Question:

How can I deal with their stubborn refusal to read my comments carefully and give them fair consideration?

Answer:

When you are the low man on the totem pole, it is all too easy to fall into an unproductive communication game with such people.  The key is to use an authoritative but not disrespectful tone, write in a neutral tone with no emotions showing, repeat yourself as needed, and time your repetitions carefully.  Note about the timing:  don't reply right away.  You may draft an email response right away, but send it after an interval of time has gone by.
There are two ways to repeat yourself.  You can choose whichever one works better for you.
(a) The succinct approach: &quot;I responded to these points in draft number.letter, submitted on date.&quot;  Or: &quot;Please refer to comments submitted by email on date, time.  Notice &quot;comments&quot;(not &quot;my comments&quot;); &quot;submitted&quot; (not &quot;which I submitted&quot;).  Depersonalizing the language you use with them helps your messages sound authoritative.)
(b) Copy and paste from the previous draft or email message.

There must be no hint of frustration or sarcasm in your messages.  You can be a broken record, as long as you don't show you're aware that you might sound like a broken record.  And you must not show you are annoyed, because with people like this, showing annoyance is paradoxically counter-productive.
It might be easier to adopt this tone if you pretend you are the right-hand man of an expert in the field, drafting a response for the Big Researcher.  (This is analogous to being a legal clerk to a big name judge.)  Write your comments and email messages as though they will be signed by that imaginary senior researcher (which might be you twenty years from now!).
These tips bring no guarantee of success.  But at least you'll have minimized the time and energy you've put in.