Resonance Veil allows you to, say, convince the IC that you're a file instead of a persona, and so on. It doesn't let you do things that require marks to accomplish (like shutting off the IC).
Marks are icons (page 218, right column, top-middleish). And from p236: "If you can show a device or host or whatever that you have the right mark, you can go where you want to go."
Resonance Veil arguably allows you to show a host, device, persona or other system an illusory icon. It's a fake stamp in your passport, a fake cover charge stamp on the back of your digital hand. It's convincing a device that something just happened in the matrix (I showed you my legitimate entry credentials) that didn't actually happen.
...but, if you disagree with that, there's still:
Puppeteer to force an "Invite Mark: 3 marks, duration forever" action (or just do the action you needed one or more marks to do).
Transcendant Grid replaces Brute Force or Hack on the Fly for hopping into grids for which you don't have access permission.
Less direct: use a sprite to cookie a legitimate new user of that sytem, get the passcode they use to access a system/be granted marks. Or possibly use Resonance Veil to convince the system that you just gave them the new user passcode when you didn't (though if you didn't agree with the RV use above, you're probably not going to agree with this one either).
True, technos aren't going to be as good at hacking actions as a decker unless they're built as a faux decker (and maybe not even then). But several of their threads and sprite powers allow them to get around the need to use hacking actions. And with threading - unlike regular hacking - costing stun damage, I think it's probably not unbalancing to let some threads (like RV and Puppeteer) replace many more hacking actions.