vintage versus modern speakers

...unless you happen across a steal somehow but most often you usually get what you pay for on the used market.

As Larryi and Almarg have touched upon the subjective impressions of some older loudspeakers compared to some newer ones, I would like to add that some older loudspeakers compare rather favorably objectively to some of the newer offerings too.
When one considers the marketplace bathtub effect of the value of some older loudspeakers, it seems as though some of these older loudspeakers offer quite a bit of intrinsic value.

Larryi makes some valid points....
I continue to hear modern speakers which leave me befuddled....yet clearly remember the original Martin Logan CLS electrostatic speakers from the '80s.....a sound (admittedly on smaller scaled music) which I have not heard reproduced by any other speaker...modern or otherwise...

I know. Myself I prefer the lovely Chevy Vega over these silly modern technology autos. I've tried simply HUNDREDS of cars, and absolutely nothing can compare with my amazingly sounding Vega. It's got the bucket seats, and AM radio and white wall tires and a 4 speed manual transmission.

People can get used to and prefer anything. And no one is saying that all new speakers are great, folks. But amazing engineers dedicating their lives to what they love, with the amassed knowledge from the 40s, 50s, 60s, 70s, 80s, and 90s, and the power of the computer for theorizing, testing, measuring, etc, all add up to the potential to build an amazing speaker. Today's $3000 speaker can sound excellent. $5000? $10,000? $20,000 speakers? I know I haven't tried them all. Are those of you knocking all modern speakers telling me you've tried them all? Because I'll call you a liar.

Now new good quality speakers are going to sound different than your speakers from the 60s or 80s. No doubt. And this is where the knee jerk reaction happens. It's different therefore it's worse. You don't remember your fave music sounding like that, so how dare they build a speaker that messes with your religious experience?

What you may be used to is simply inferior sound. You're stuck there and happy. You couldn't imagine that your speakers and or ancient gear(not even in spec anymore) is coloring the sound. Stay there if you want, knock yourself out. But don't expect everyone to not get a puzzled look in their eye when you start talking about your amazing Vega again.

The OP asked a generalized question. I will repeat here question here...

are great vintage speakers (Infiniti, JBL,Sansui, Sony, etc..) from the seventies better sounding than what is available now?

I am in the camp that says no. As a whole, modern speakers using technology derived from over the decades are much better today than what was generally available then. There are specific model exceptions, then and now, but OP asked a general question.

No different than asking if Vintage Audio sounds better than Modern Audio.

I think we sometimes let nostalgia get in the way. We can blame American Pickers for that.