longarekel, i basically agree with everything you said. i just want to add 2 points:
1. the daf yomi system has been elevated to such a madreiga that many people actually consider it the highest form of limmud hatorah. the result is that many people who can/should be able to learn much more (both in terms of breadth and depth) simply remain in the daf yomi system, blowing through masechtos, and never fulfill their potential.
2. on a related note, a big factor in the popularity of daf yomi is artscroll. now anyone can easily jump right on to the daf yomi train. while i admit that this is great for those wtih no background and would otherwise never be capable, there is a whole generation of people who continue to learn with artscroll instead of ‘graduating’ to the real thing. besides the obvious absence of ameilus batorah when learning from artscroll, many, many people are never going to acheive their true potential in torah learning because its just so easy to pick up the artscroll. i’m embarrassed to say that i know several people who are referred to by others as ‘talmidei chachamim’ who would break their teeth on a gemara without artscroll. its really just sad. again, i am all for opening up torah to everyone (like the gemara where they added 400 benches to the yeshiva when the entrance requirements were loosened), but we need to recognize that while artscroll might be a ‘sam hachayim’ for one person, it might be a ‘sam hamaves’ for another (in the sense that it is preventing them from reaching their potential)