I hope you realize you just described the entire Internet. Which is the ultimate irony of complaining about the security of tor: you're trusting someone else to forward your packets. Yes, yes they can modify the traffic to and from your host, and yes, yes they can monitor everything you're doing. The difference with the non-tor Internet is that it's far far easier to do that.
You're absolutely correct in that it is a trust issue. However, when Comcast forwards my packets they have both a profit incentive to not go stealing my all of my credit card info (their customers would quickly take their business elsewhere) and a legal incentive (they're a known entity inside the US - someone's going to court). With Tor, I'm putting all of my trust in someone likely on the other side of the globe who has only given me no more identifying information than an IP address and promises no more than that they'll offer me free bandwidth. That person could have set up shop a few hours ago and may be gone tomorrow.
And what if they did sslstrip your connection to your bank's website? Would Tor catch it if the exit node only did it for a week or two and only to .5% of the connections? Would any of the victims be able to determine the source of the attack? How many people on Tor actually keep track of what exit nodes their traffic is going through?
How many people keep track of the route their packets take? (Dare I say none?) How many third parties will it pass thru? (Many). How many of them can trusted to not monitor you (this is why ssl and even ssh was invented), how many have adequate security controls to prevent data theft (again this also why ssl and other tools were invented), how many can be trusted to not forward your data to a hostile government, etc.
It's the same problem, trust. And since when was the internet considered a trusted network? Calling out Tor for inherent trust issues with the path is ironic, neither the internet nor tor is a trusted network. Tors solving a different problem: monitoring. Both have the same problem which neither solves: tampering, but other technologies do (ssh, TLS, etc.)
In both cases, you shouldn't trust a third party (or an intruder into that third parties network) to either not modify your packets or to respect your privacy. At least tor helps with the later, the former isn't solved by blindly trusting an ISP or assuming your entire route is trusted (NSA anyone?).
Trust no untrusted network. At least tor is Upfront about this.
What's the point of using Tor to access your bank's website though? I don't think that is a normal use case at all because there's no point using an anonymity network for that, because your bank probably knows who you are. Exactly the same as with credit cards.
If you're going to pay for something over Tor, it should probably be with a prepaid credit card (or bitcoin). And if you're buying something anonymously then you know you're taking a risk.
Same as with email accounts or any other account. It doesn't make sense to use any account through Tor that you've used outside it, as it could already be identifying information.
Or many customers in the US. For most consumers you have one choice of broadband provider due to local government monopoly grants. It's either comcast, or verizon or another big telco/cable company, but rarely is there a second equivalent option.
