I tend to agree with this line of reasoning. For a guy who was undrafted, he's done amazing but there has to be a reason he went undrafted and I think Romo might have just hit his ceiling as a QB.
When you examine his total game--mental, physical, leadership, clutch gene--he's an average QB. That's it.
I actually think he's pretty similar to Big Ben. Both of them are decent QBs but they are only as good as the talent around them. Both have the ability to win a game here and there but can't really do that consistently week in and week out. The difference is that Big Ben plays for a much better organization and has had the talent around him to win 2 Super Bowls.