@MartinC
I see your point, but it's a bit funny that you are yourself a good counter-example since you DID have a dangerous pet line ready in 7...0-0 (incidentally one of my favorite blitz openings)
In any of the Classical with 7...Qb6, the Classical with 7...Be7, the MacCutcheon, the Winawer PP or the Winawer 7...0-0 I would absolutely not want to be White without serious preparation.
With 3.Nd2 on club level you will often meet French players with only a hazy idea of either playing with an IQP and often doing so too passively, or playing 3...Nf6 4.e5 Nfd7 and attacking White's centre with standard moves like ...c5, Nc6, Qb6, f6 etc. In the latter case the result is the following main line:
1.e4 e6 2.d4 d5 3.Nd2 Nf6 4.e5 Nfd7 5.Bd3 [5.f4 could also be good on club level, if White is aware of all the possible ...Nxe5 sacrifices)
5...c5 6.c3 Nc6 7.Ne2 Qb6 8.Ndf3 cxd4 9.cxd4 f6 (I also often see 9...Bb4+)
10.exf6 Nxf6 11.0-0 Bd6 12.b3 0-0 and here either 13.Bf4 or 13.Bb2 give White comfortable play and good chances for an edge.
PS Of course theoretical knowledge on club level is often modest, but one thing that amazes me is the number of people who play the Najdorf (!) of all openings with little concrete knowledge. Probably they saw Fischer, Kasparov or Topalov play it and concluded it must be great, but still playing it without theory is insanely risky imho.