Let's put this in perspective.

Lots of programs we use every day depend on so-called "external software", some of which are add-on Microsoft components (e.g. .NET), and some of which are third party. It's not ludicrous, it's standard practice. Flash itself is used in many web sites and applications, and is a more or less ubiquitous plug-in.

My advice would be to focus your attention on sorting out the issue with Flash on your computer. That's the cause of this problem, not Poser.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)