I don't think that being able to replace a library at runtime is a useful enough feature to justify the high maintenance cost of shared libraries. Like I complain about in a comment below, the cost of shared libraries is that an upgrade is all-or-nothing. If one program on your system depends on a quirk of libfoobar-1.0.3, and another program on your system depends on a quirk of libfoobar-1.0.4, you're fucked. You can't have both programs on your system, and Linux distributors will simply stop updating one of them until the author magically fixes it, which happens approximately never. And, the one they stop updating is the one that you want to update to get a new feature, 100% of the time.
It's just not worth it. A binary is a closure over the entire source text of the program and its libraries. That's what CI tested, that's what the authors developed against, and that's what you should run. Randomly changing stuff because you think it's cool is just going to introduce bugs that nobody else on Earth can reproduce. Nobody does it because it absolutely never works. You hear about LD_PRELOAD, write some different implementation of printf that tacks on "OH COOL WOW" to every statement, and then never touch it again. Finally, dynamic loading isn't even the right surface for messing with the behavior of existing binaries. It has the notable limitation of not being able to change the behavior of the program itself; you can only change the results of library calls.
I never want to see a dynamic library again. They have made people's lives miserable for decades.
It's just not worth it. A binary is a closure over the entire source text of the program and its libraries. That's what CI tested, that's what the authors developed against, and that's what you should run. Randomly changing stuff because you think it's cool is just going to introduce bugs that nobody else on Earth can reproduce. Nobody does it because it absolutely never works. You hear about LD_PRELOAD, write some different implementation of printf that tacks on "OH COOL WOW" to every statement, and then never touch it again. Finally, dynamic loading isn't even the right surface for messing with the behavior of existing binaries. It has the notable limitation of not being able to change the behavior of the program itself; you can only change the results of library calls.
I never want to see a dynamic library again. They have made people's lives miserable for decades.