TOS wasn't so much hampered by imagination as it was by budget, resources and time. The transporter is the prime example of coming up with a more affordable solution to not having to land the entire ship, but also to get the characters into the story faster.
The show's designers were also hampered by their limits of perspective and extrapolation. There were developments in the years to decades to come they simply could not foresee. And this is true for any SF production be it film or television. LCD and LED readouts were still a few years in the future for the general public. Interactive displays (such as tablets and smartphones) were decades in the future. There was probably very little in existence at the time to give anyone but a genuine visionary any idea of what was to come. Mind you they did foresee flatscreen displays even if they figured it was still a version of the CRT. But in "Requiem For Methuselah" they did have an actual thin flatscreen display not far removed from what we might see commercially in the next few years.
TOS was smart in not over explaining their tech and hardware. To some extent that allowed it to age more gracefully since new rationalizations could be applied without really contradicting how we saw the tech used. I do find it amusing that TOS is credited with imagining the cellphone, but it's an inaccurate representation because the TOS communicator is definitely not
A cellphone needs a supporting network infrastructure to work while a communicator is an independently operating transmitter/receiver (and possibly translator) with a range in tens of thousands of miles.
There's also the fact that I don't assume TOS reality is ours and that was illustrated right within the series itself given historical inconsistencies with our own history.