I think it's fine. People who have been using GTD for a long time may well also have all those lists. I would suggest:
- From time to time, go over "someday/maybe" and decide whether to move things from there to more active lists. This is normally done periodically, e.g. at each weekly review.
- Your "errands", "calls", "online" etc. are presumably next-action lists. When you get a chance, e.g. at your next weekly review, you can go over them and consider whether you want to move anything from there to "someday/maybe", e.g. if you're not planning to do it in the near future. Also, make sure each item is really a single, physical next action that you know how to do and don't need to do anything else before. From time to time, you can recheck these lists to see whether any insufficiently processed "stuff" has crept in -- for example, if something on an action list isn't getting done for a long time, it could be because it isn't defined clearly enough as a single physical action.
- Inboxes such as email inboxes will tend to be there continuously. You can process each inbox when you have time, and perhaps at weekly review check whether you have any inboxes that aren't getting processed.
I don't think it's necessary to collect everything in one big list. I think that idea was designed more for people who hired David Allen to help them get all organized over a single weekend. I implemented GTD more gradually.
The main thing is to make sure that eventually, everything that should get processed gets processed.
Inability is an abstract thing involving comparison with alternate universes; it cannot be experienced.