I am not that familiar with Revox to make any relevant comments, but as for the Tascam 34, lets start by clarifying its not a 1970's
made unit, the Tascam 34 came out in 1982, it was the followup to the Teac A-3440 (which is the model I have). The A-3440 came
out in late 1978/early '79 and was still produced after the 34 came along.
No one can dispute these open reel machines are outdated technology in comparison to all the digital recording products that we have at our disposal nowadays. In other words, yes, a Tascam 34 is forty years old. However, to put forth the idea that these vintage units are useless or worthless based on
your own difficulty with them seems misguided.
First of all, if they have been sitting in storage for a long period of time, its unrealistic to expect they should spring back to life and work perfectly when you suddenly felt the urge to try them. Even so, despite that, they seem to be playing normally from what can be seen in the video.
The main thing you complained about seemed to be your frustration with mic levels. If you had an A-3440, you could plug mics directly into the front panel, however, these units are multitrack machines and were intended to be used with a mixing board, (when the Teac A-3440 came out, it was offered along with the matching Model 2A and MB-20 meter bridge).
You dont necessarily need a Teac/tascam mixer, or even a vintage one, there are so many of them available nowadays, to which you can simply connect an or all of your mics and setting the levels would be very straightforward, and the mixer then interfaces with the recorder.
Nothing wrong if you dont feel vintage equipment has much to offer to You anymore, but thats not to say that the same thing applies to Everyone else- especially in this particular forum, thats dedicated to Analog gear.