What are the problems of Avalanche?

I'm curious about Avalanche, as it's gaining quite some popularity in the crypto sphere. Could you please elaborate on some of the challenges or issues Avalanche might be facing? It seems to have a robust infrastructure, but I'm sure there are areas where it could still use improvement. For instance, is scalability an issue? How about the cost of transactions? Or perhaps, are there any security concerns that we should be aware of? I'd really appreciate a comprehensive breakdown of Avalanche's challenges, as it would help me better understand its position in the market.