On the SU1492 thread, someone suggested an emergency system to lock all the overhead bins, activated by the crew, in case of an emergency landing, which I'd like to add, could be used at all landings, because people tends to stand up and take their luggage before the aircraft has even stopped from the landing role. It could be a good idea. But the best idea was not allowing so many things (better: not allowing anything besides one very small item). And making checked luggage free of charge again.
Certainly, boarding is now a mess, takes much longer than before. Also leaving the plane. Because many times, people have their luggage in a different compartment than the place where they are seating, and that's due to A) There are a number of containers occupied with airline material or crew luggage, and B) there are more bags than seats in the plane. And is not only bags: you have tons of duty free products (including bottles, very fragile), you have coats (in winter), etc.
Larger items of hand luggage are often cause of delays in the boarding gate (because ground crew has to say it doesn't fit, and people always complains). And also on security inspection, which after 9/11 is well known for being slow, but now is slower.
Low cost carriers started charging for luggage in the late 1990s, so people decided to take hand luggage instead. But since 2015 approx, main airlines (in Europe) started charging also for luggage, and now they even do it intercontinentally since 2018 approx. Some people, few, defend this policy saying: now is cheaper to fly.
But the problem is: we have too many things inside of too small aircraft, too full of people, and the manufacturer (maybe) hasn't taken into account this situation when planning the evacuation of the aircraft...
Also, I believe airlines had often problem (still have) loosing luggage, or with stolen items (very common in Latin America). That's why they prefer people having all of their belongings with themselves: that means no responsibility. Also no responsibility if it doesn't fit, if it has items not allowed by the TSA, etc.
Some things will have to change, specially the screening process of luggage (a friend of mine, who was asked to send her hand luggage down, on a very busy FRA-BCN flight, was stolen over 15.000EUR of jewelry: the police @BCN didn't feel like filing a report, airline never paid anything...). And specially the speed on which luggage is delivered. But the technology is there, and airports are each day more efficient.
BAA spent 1bn GBP on the baggage system at LHR-T5, which is now not often used as most people has hand luggage! So it was a waste. But the system is there, and it could/should be used to the 100%.
Items of hand luggage, are not only uncomfortable (for crew and passengers) and create delays, loosing take off slots, BUT they (could) and now be considered deadly, as we see 41 people perished on a Russian airliner.