4D batteries just doesn’t make sense in 2024. That was for incandescent lights, modern LEDs are brighter and use a small fraction of that power. You could still have the form factor if you really wanted a giant flashlight for self defense or something, but a pair of AA’s if you really don’t want rechargeables would be more than enough for a long life flashlight.

But any LiIon battery is going to far outperform alkaline batteries.