I wouldn't really say that. I mean imagine what people said about last year and Frankfurt versus Barcelona, we have seen how they managed to win anyway. Which shows that they are not really that bad, I feel like this is also the same thing.
I believe that we shouldn't be really considering this as a problem and maybe Napoli could win and wagering on that would make sense and all, but it is not a guaranteed thing. We should wait and see how it will happen and that way we would be a lot better ready. The game is nowhere near as well, maybe something will change, some people will be injured, booked or whatever and we should be ready for it.
You have a point of course. Frankfurt were the underdog against Barcelona last season but they surprised people by eliminating Barcelona later on. On the other hand, it was the Europa League. Barcelona's financial condition was also much more decent than now. They didn't make a very big effort to go for the Europa League title as a result. Because a team like Barcelona wouldn't care about the Europa League title much considering their quality level. There should be a reason for them to fight for it for real.
When it comes to the Champions League things are much more different. This is the biggest tournament among all the European tournaments above all else. None of the teams has the luxury of not caring about it. Napoli have had a great run so far here also. Frankfurt have impressed people maybe but they had better be prepared for their biggest challenge so far. Otherwise Napoli can tear them apart