This is a crazy situation, and thankfully there looks to be a class action lawsuit against Apple regarding this "iMessage Purgatory" issue. Not sure where it stands, probably nothing will happen.
I just switched to Android, and missing texts from iPhone users was an immediate and aggravating issue. Alas, I was in iMessage Purgatory. I was able to disassociate my number from my Apple ID by turning off iMessage on my old phone. This fixed direct text messages, but not group messaging. I just simply cannot rely on getting group messages when multiple iPhone users are in the group.
In my case, if I am in a group message with other iPhone users, I stop getting messages (sometimes). This seems to be because the iPhone texts switch over to iMessage, and the messages never make it out of the Apple iMessage gateways to the SMS systems. Worse yet, the iPhone users see a blue message (meaning iMessage, green is SMS), and receive no failure message. So, they think I received the text successfully, and I have no idea they even sent one.
There is a setting in the iPhone, SETTINGS-GENERAL-MESSAGES->SEND AS SMS, this is supposed to forward texts to SMS if iMessage is unavailable. It was disabled on about half of my friends' iPhones. Switching this on does not seem to have fixed the issue, although Apple did recommended this. Besides, are you going to call all your contacts and explain to them that they have to enable this setting? Seems unreasonable.
So, it's not your phone. It's Apple's iMessage architecture. Will it be fixed? Probably not. But, there are 2 possible hypothetical solutions I can think of:
1: Apple fixes their iMessage architecture to ensure group and individual messages to non-apple devices don't get stuck in iMessage purgatory. They could send also consider sending non-delivery receipts, just like you get if an email fails to a recipient. This would be ideal.
2: Apple releases an iMessage app for Android. This would be OK, but it means Apple forces masses of users over to their proprietary system.
Both are unlikely.
Another solution include using 3rd party, platform independent messaging apps, like WhatsApp. But, you cannot reasonably expect to convince all your personal and professional contacts to download and use this app just for your convenience.
There is, in my opinion, a reasonable expectation that simple direct-text and group-text messaging should work no matter what the provider/platform. iMessage conflicts with this expectation.