Is this set in the 70s?

I wondered that too. They seem to have modern technology, they have MRI machines, but David's girlfriend in the flashbacks is dressed like mid to late 60's then Oliver Bird looks very 70's, and he asked if girls still go braless and are into "free love". David said, no, Bras are back now.
The cars aren't vintage, that I have noticed. The way they were "vaping" drugs looked modern. I want someone to sell those frog vaporizers. LOL
It seems to be a mish mash of time periods.

It's intentionally vague and ambiguous so as to give the viewer a more off-kilter look at the world, perhaps in the way David would see it. I believe Hawley said they don't want to have to be tied down to a specific time or era and it certainly does seem to be an effective way to throw the audience off balance a bit!

Well, everything seems outdated for today's standards, so my answer's going to be... no. (it's a trap)

Melanie's husband who's been absent for 20 years looks like he's stuck in the 70', and that could be some kind of a reference point.