I would not call TN's offense "gimmicky", and I'm not sure where that description comes from. All spread offenses seek to spread out the defense and get favorable isolation matchups for playmakers. In that way, TN's is not different. Josh Heupel is simply using his version of a spread offense, with WRs split very wide so safeties can't help until the receiver runs to the 3rd level (if then). The quid pro quo is that his split receivers are not in a position to block for the running game. But since Heupel's offensive sets usually force safeties to play deep, that means TN is running against 6 or 7 man fronts. If your WRs are your best playmakers, this is not a gimmicky approach to use. It is actually pretty smart. TN's problems are on the defensive side, although you couldn't tell it when we played them.
Historically, every new offensive wrinkle gives way to a new defensive wrinkle by some clever DC on the schedule.
Under Heupel, TN's program has been heavily involved (both directions) with the transfer portal. So it is hard to predict how good TN will be from year to year, although people assume they will be good again in 2023 because they were good in 2022. But that doesn't necessarily follow, and I can point to SEC teams like AR, TX A&M, and MO that surprisingly struggled in 2022 despite higher expectations.