That doesn't seem to be the case with the 785 but the 795 certainly uses a proprietary stem (who doesn't btw).

I have a 2009 Look 566 Rival. BSA threaded bottom bracket. This bike has at least 12K miles on it (I know, not much by Bike Forum standards) and looks and rides like brand new. I have upgraded the wheels to Spinergy tubeless and rear derailleur to handle a wider range cluster bringing it more up to date. The bike still catches attention due to its rarity. Just as happy riding this bike as my titanium.

I had a Look 765 1x. Liked that bike a lot but sold it to get a Lysnkey titanium.

I think most of it comes down to rarity like 1Lieutenant mentioned. I don't see why their bikes wouldn't be enjoyable to ride regardless if you went their base model to their insane top models.

Yes I have, right before posting. Have you? Every higher end road bike sold these days uses a proprietary stem/handlebar and seatpost these days, that's not something you can really call Look out for. Also, none of their bikes use the (excellent) proprietary crank any more. My point stands: Look has never gone to Venge/Madone/System Six levels of proprietary ridiculousness.