This questions always pops up when dealing with the more elderly of the sempais/peers. By this, I mean ppl in their 40s who are less fit and able to perform rigorous ukemi.
Ok, I'm in my 40's, have my share of injuries, and still try to perform the best ukemi I can. I know quite a few aikidoka who are older, and do the best that they can. I think you might be confusing taking care of your body as needed with 'us[ing] their senpai status' or 'riding on the coattails of the cultural capital...'. If you connect those two things, you may find yourself being rather judgemental about the performance of someone who has the need to get up the next day and go to work. While I'm sure there are those who confuse these issues themselves (to their own advantage in an egotistical sense), I'd be carefull about overgeneralizing here. Just my take on the statements provided. I also know many 'younger' people who might fit into both or either of the categories you mention.