I don't think anyone was bashing your methods. They were just making sure that you knew the importance of flushing and you obviously do.

It is way more difficult than most people understand to get all the debris out of a system with flushing. It is also sometimes a problem because a little flushing agent is left behind. From your description, it sounds like you are doing a very thorough job. I have seen very thorough jobs not be enough. Given your frustration level I really think that a suction side filter would be worth the trouble. It's not that big of a deal to add one in the line and it might just be the "Silver Bullet" that you're looking for. Sometimes when a suction side filter is not used, the new compressor ends up being the suction side filter and then the cycle repeats itself.

Best of luck with it.