You're comparing Apples to Oranges here and simply it's going round in circles. 701s have been in far longer storage than GA and WMR units you keep mentioning, faults and various other issues on those stored units whenever they come out of storage have yet to then be found thru trial testing before becoming anywhere near passenger acceptable.
Hence why there is only a mere handful of the units out and about carrying passengers. The only comparable similarity to other Aventra TOCs is how poor intial Aventra reliability is, which will only improve(rather painfully in several cases minus again GA and C2C) once there is units running about and basically failing here and there to have faults identified and fixed.
If you'd like to get out one of the 701s that have been stored in the salty air of Marchwood for a long time to see how acceptable, condition wise it is then go ahead

Hence the process of passenger ready trials even if its been painfully slow due to other factors well discussed in this thread.