[{quoted}](name=Vlada Cut,realm=EUNE,application-id=LqLKtMpN,discussion-id=bm2kcnr9,comment-id=00040000,timestamp=2019-10-20T19:51:59.496+0000)
No, that's a feature, it is an AA like spell but not an auto attack empowerment(that's why they chose to have it AS scaling so it can behave like an actual auto attack late game), so the spell will be able to get recasted once Shen's W Jax's E or Teemo's Q effects are gone or until Garen's Q cast time expires and goes on CD.
Just like Ezreal's Q, Gangplanks Q, Illaoi's W, Jax's W, etc. are all spells that act like basic attacks but aren't really? And they all get blocked? Not to mention that Garen's Q did go on cd the moment he attacked pre-rework, and it's even said on the league wiki that it IS blocked by AA-blocking abilities. Also, have you actually read the skills description? It quite clearly states that, and I quote: "His next basic attack within 4.5 seconds deals 30(+100) physical damage and silences his target for 1.5 seconds."
TL;DR: A lot of other champions have abilities like Garen's that DO get blocked. His Q USED to get blocked. The wiki says it gets blocked. Q's description clearly states that is an auto-attack empowerment.