Ok. So if I'm a type 9 and interdicted by a pirate in an ASP I'm toast. So be it, I'll learn that that's the case and pay up.
What if I'm interdicted by an eagle? Perhaps my weapon loadout lets me win that battle, so it's only the beefier pirates I have to worry about. That's a reason to tool up - to win some battles, not necessarily all of them. And if Solo beefs up the rate and difficulties of NPC interdictions in low-security systems, those defensively equipped type 9s are going to fare better than the pure cargo box with an engine attached. I would hope that a weaponised type 9 with shield cells and a good pilot would have some chance against a wing full of 2-3 NPC pirates in small ships.
You can't refute an entire discussion by focussing only on the case where the pirate is in a ship which is more than capable of handling you, and ignoring the cases where that defence _will_ let you win.
No one is pirating in an Eagle, it can't hold an interdictor, a shield and sufficient cargo.
Assuming someone would actually do it, right now you can submit - charge FSD and run out before your shields are down - assuming the Eagle isn't specialized in taking down shields and you run an A-rated one, I wouldn't count on that - but even if your shields go down, you will get away before suffering significant damage.
However, that is currently not working as intended, submitting to a hostile interdiction should not give you back your FSD within 5 seconds. Once FD fixes that, even an Eagle will be a threat to your Type 9.
Why can I not limit the discussion to the Asp vs Lakon argument? It is the most important one, because almost all pirates are in Asps at this point, and they are primarily targeting Lakons for these reasons, with other Asps coming in on fourth place. Why should we discuss the super theoretical Eagle vs Type 9 scenario when that scenario doesn't happen? Pirates will pick what they can take down.