Normally in correct aikido practice the ratio of successful techniques should be not higher than 1 to 50, it means that 49 tries you should fail miserably to get one technique working OK (doesn't mean perfectly of course..).
Not in any dojo or in any field in which I've actually learned anything.
I don't know of any endeavor in which a person is supposed to learn by being unsuccessful 98% of the time. You have to be allowed to develop the gross movements by practicing them fully, not by being repeatedly stymied in them.
Others have posted here the very apt analogy that you cannot learn to drive if every time you start to press the accelerator the instructor hits the brake.
I've heard it suggested by others who are very good teachers that 80-90% success rate is what slowly develops knowledge and ability, the proportionally much smaller failure rate being where the manageable challenge to hone skills lies.