Do we really need anything greater than 24/96? Opinions?

https://images.app.goo.gl/KSJhYUn3eiAAnhav8

OK, study this image in the link above.
It displays what we can hear in dB and in frequency. From the softest sound we can hear from 20 to 20k hz. And up to our threshold of pain!

As seen there are a area of "music" that is smaller than our ears can perceive.

Now it is that the softhes/lowest of audibility of our hearing is most likely done and measured in a anechoic chamber were it is "completely" silent.

When we do not capture music in anechoic chambers where it is completely silent it is understandable why the music area is smaller. And for example starts at 30 dB as their "silent". In their environment.
And max sound pressure is 100 dB in the chart. (What musicians ar willing to jam at their threshold of pain, so it is understandable that we have some headroom there also.) :D

So everybody can easily see that ~70 dB of dynamic range from the softest to the loudest sound pressure for music performance at the most.

24 bits digital audio has 144 dB dynamic range. 
24 bits has the double dynamic range that of music has and also more than humans can perceive (even if we are in a anechoic chamber). But we are not and listen in silent rooms that has >=30 dB of noise. ;)

So regarding if "we really need anything greater than 24" then for the bit dept is the answer: "NO".

It is a interesting image that if we want to be able to hear (not just feel) 20 Hz then we most likely will be able to succeed if we play close to 120 dB! :)
We can also see in the other end 20k Hz it is 100dB (if we are young).. Then those who are familiar with how a real implementation of a loudness control works and the science behind it that this image has something in common with that implementation. (As a reality check to see that the information in the image is OK..) :)  

    

No I am not a measuring guy. :) 
But I realize that my previous post sounded like one.. :(

The point with it is to point out some levels and real numbers to get a perspective of what we are talking about. When 16 bits CD bit depth is 96 dB of dynamic range.

We do not always understand what that really mean and we go into the trap and think but 20 or 24 is better and it is better to be safe than sorry. ;)
That we have already with a wide margin achieved at 16 bits.

Now I do not say that CD is be all end all, but there is other factors why a format do not sounds to our liking. But it is not whether it is 16 bits or 24 bits. That specific part is irrelevant.  :)

"We are probing the future generations. Unfortunately, but a lot of them have no real future. "
Right, so you are AI from the future and  you were after probing your future generations, so you are simply lost in time! This is 2019, and we are your past generations! So nothing is lost, just reset your PlanckTime clock and go back to the future. Or to the future past your future. Then you can fix the generations for their future future past your future.

@optimize, "But most of us thinks that more is better.
A analogy is when you parallel parking your car. The car is the whole recorded music and the space you want to park your car is the format.
If you have a big space it is easier to park but if the space is 10 m long your car (music) is still 4 m and there is 6 m of unused space. You don’t have a longer car because the space is longer.. :)"


A great analogy, and one's that easy to understand. 

The OP is correct when he says,

"Plus, I really think the recording (studio-mastering) means more to sound quality than the actual output format/resolution. I've heard excellent recorded/mastered recordings sound killer on iTunes streaming and CD." 

If you are looking for genuine sonic improvement over Redbook then remastering is where that dog is (sometimes) buried.

Masterings can and do vary considerably in end result, and this does nothing to clarify matters. For example if you were to buy Bob Dylan's Street Legal album you would be faced with a number of buying decisions before you could be sure you had the best sonic copy as this quote from Wiki makes clear. 

"The original 1978 LP credits mastering to Stan Kalina at CBS Recording Studios NY; the album was produced by Don DeVito. In 1999, Street-Legal received a special remixing and remastering job from DeVito. The newer version boasted richer sound, correcting numerous issues with the original production. The new mix was also used in a 2003 SACD reissue of Street-Legal. However the original 1978 mix was reinstated for The Complete Album Collection Vol. 1."

It all depends upon who did it, what with, and why?

For what it's worth I'd take the 1999/2003 issue over any of the others.

In my private ranking of the sound quality factors recording/mastering is third, after ear/brain and loudspeaker/room systems. And before electronics.