Ooh, math. Ok. I'm going to say now that I have NO agenda as I post this; I'm typing all this before I start to even THEORIZE the calculations.
Towers have, at their most durable, 70 armor and MR. It's worth noting that they ARE susceptible to armor pen and magic pen effects. For our purposes let's ignore that. Now, envision a character with 250 AD and 1 AS; it can be Talon, if you want. The Outer Turrets have the most health, so let's say that's the one we're talking about, with 3500 health. Each auto deals 175 damage to this turret, taking 20 seconds to destroy, without counting minion damage because there's quite a bit of randomness there. Let's just say that, if uncontested and with a big enough wave to allow, it takes this hypothetical character 16 seconds to destroy. That's...actually not terrible. 16 seconds is plenty of time to react, either by moving mid to top or by moving somewhere else on the map to get value out of it. And I mean, 250 AD and 1 AS is either a mid-game carry or later-than-mid-but-not-quite-late-game juggernaut. If someone worse than that tried it, that's way more time.
But hey, I said I don't have an agenda, so let's look at LESS durable towers. Give them 50 armor and MR. Of course, that means its earlier in the game, so the character in question might only have, say, 180 AD and .9 AS. That character takes 64 seconds to take the turret uninterrupted (by the way, I just checked, and 180 AD is ABSURD here, because outer turrets have 50 armor at eleven minutes; if you have 180 AD at eleven minutes, please add me as a friend, I need to climb ranked)