Why are group text messages failing when an android user is part of my group message?

There are two very different types of messages.

What is the difference between iMessage and SMS/MMS? - Apple Support

It sounds like your group is a mixture of SMS and iMessage recipients, which certainly complicates the process.

See especially “If you have issues with a group message” here.

you can't send or receive messages on your iPhone, iPad, or iPod touch - Apple Support

I am also having this issue and the solution you referenced was not helpful. It would require me to delete every group chat that I have that includes android users I would effectively have to lose years of conversations and history with close friends and family. It’s a ridiculous solution.

I think the main issue after looking through recent posts is that this appears to be an issue caused by the recent updates. There’s varying advice and suggestions to resolve the problem but no one is addressing this as a wide spread issue. I tried the solution you suggested and it didn’t work. I’m also seeing advice to contact my carrier because they control SMS messaging, however I’ve talked to people having the same issue who are with other carriers.

Of course, you’re not required to save these conversations as text message threads. You could, for example, save them as screenshots. Or seek some third party application to perform this chore.