There are many scenarios where Qantas Club makes sense. As you say, visiting about 12 times a year is a good number. That's just six domestic return trips, and in my case, that's most likely to be Brisbane to Sydney or Melbourne.
Best case scenario on a Red eDeal is 180 SCs from that travel, and that's if it's all Melbourne where the earn rate is highest. Even with DSC, that's 360 SC total - but in my case, unlikely, as I can't race out and book a year's worth of travel in a week, as I simply don't know what I'll be doing and when. 360 is nowhere near earning or retaining Gold: but in this case, for just $270, I can make the experience much the same as Gold - and on a per-trip basis, that averages out to $22.50 per departure. By the time I've had a meal / coffee in the lounge, I've got my money's worth, so it works for me.
You mentioned extra baggage - and with Qantas, you do actually get that as Qantas Club, so again, less difference to Gold. You get priority check-in too, and in Brisbane, you can use Premium Lounge Entry, which is the domestic terminal's only active priority screening lane.
You also mentioned complimentary seat selection as Gold (presume you mean international) - but it's long been free for Silver too, and now if you book direct on the Qantas site, it's free even for Bronze. So again, less appeal for status.
On higher upgrade priority, not something I really need as I prefer to redeem rather than upgrade (which means I earn more SCs as a Points Club member), but each to their own.
I guess the use of Qantas Club is best with those who travel more than just occasionally, but not enough to reach Gold where you get it for free.
In my case, I'm currently both Gold and Points Club Plus (which grants free Qantas Club anyway), but know that won't be the case forever, so it's nice knowing that even if I lose both, I'll still have lounge access for the years beyond at a very cheap price.
