A good chunk of chaos in Rails apps is caused by people who either insist they know better than the out-of-the-box solutions, or they “just prefer it my way.”
ActiveRecord can both offer fast development and create issues (especially those that only come to bite you later). It exists in a multi-faceted environment. Tradeoffs, as always.
I think most would agree. It is the "doesn't make much sense" part that we're discussing, though. How does it not make sense when you seem to have the same opinion of it? It seems, as an onlooker, that it makes perfect sense to you.
Well, what remains of Rails or of ActiveRecord once you remove the part that's done outside the database? It just seemed like a very shallow view of what rails is.
It is just not tenable where latency poses a practical constraint under an implementation that is not theoretically sound. There are plenty of hacks to work around it, though, so it is not really a problem in practice. To call those hacks to work around a system with shortcomings "using the database properly" is a bit of a stretch, though.
Just so we're clear, the use of JOIN, IN, etc. are not hacks in and of themselves. They serve a purpose even where latency doesn't exist. But when applied to solving the N+1 problem, their use is a hack. Again, one that gets the job done and solves the problem – hacks aren't bad, but is not theoretically sound. If you did not have latency constraints to contend with, you would not prefer it.
The better question is: Why use a database that sucks? Latency periods are small enough in SQLite, for example, that you don't have to worry about the N+1 problem in any real-world situation. It doesn't have to be a problem in need of hacks.
Previously, ActiveRecord gave newer programmers a legible, fluent interface to the database in a language they already knew. So instead of learning SQL, we abused the heck out of AR. I think that the industry, and rails itself, has matured since then and I see a lot less of this nowadays.
EDIT: I'm not bothered by this, but this is a very odd comment to downvote. What on earth is so offensive or distracting about saying someone else is likely more knowledgable than you are? Very confusing.