Thanks so much for your feedback!
1. In your cover letter quickly describe one/two thing(s) that you have done that is relevant and might open a dialog for further discussion. Or peak someones interest at least.
2. Try reformatting your resume to be less about chronological order and more about skill set and tasks you have done. Use bullet points for libraries, API's etc to help bulk it up and make it obvious what you have worked with. Just don't ever lie.
Option #2 is what people with only a little or people with a lot of experience generally use because chronology puts an age on our head. Personally, I have seen that many people immediately calculate my age after seeing that I have been in industry for quite a while. Sometimes it is funny to watch/hear, other times it is just sad as you literally can watch their attitude flip, same goes for when you are young too. It is just human nature to some degree.
I am interested to get into a face-to-face conversation with a potential employer, because I sound significantly older on paper and I'm curious how that'll affect the interaction.
I always was trained and believe that you use the cover letter/email to highlight things your resume glosses over because none of us could describe everything we do in each tech role, or resumes would be 50 pages. So the cover letter helps to fill in the gaps, but sadly it just doesn't seem to get read now. I will say at least not consistently it doesn't get read, as I am sure there are more people like us that appreciate them.
And in the end it is a numbers game, as sebg pointed out, rinse and repeat.
I highly recommend customizing each note you send with your resume, don't ever use a "form" style. In the past I would even sometimes adjust my resume to highlight specific skills that are relevant, but that usually comes when you have a lot of varied experience and you need to draw peoples attention to specific skills.