What are the problems with Polkadot?

I'm curious to know about the challenges facing Polkadot. Could you elaborate on some of the key issues it's currently grappling with? I've heard rumors about scalability concerns and interoperability challenges, but I'd like to hear your professional opinion on the matter. Is Polkadot's architecture capable of handling the demands of a rapidly growing ecosystem? What about the security measures? Are there any vulnerabilities that might pose a threat to its stability? And finally, how does Polkadot compare to its competitors in terms of addressing these challenges? I'm eager to learn more about these issues and understand the bigger picture.