Wire nuts are terrible. They are unreliable, inelegant, and difficult to use correctly.
Last year I discovered Wago Lever Nuts and I will never go back. These wire connectors are amazing. They can be used for all of your home and industrial wiring in lieu of wire nuts, and are also useful for many other hobby wiring projects. They are of course properly certified for in-wall AC wiring.
You can mix and match different gauges of wire from 28 AWG up to 12AWG, and you can individually lock and unlock each wire into the nut by closing or opening a lever. You can also mix-and-match solid copper and stranded copper wire in the same nut. They hold up extremely well under vibration, so they would be good for automotive use as well. No other wire connector is this versatile.
Best of all, unlike so many modular European industrial electrical items, this one does not break the bank. They are competitively priced to other connector solutions and the 2 and 3 circuit nuts are around $0.25 each in small volumes, and around $0.50 for the 5 circuit version.
One of the only problems is that they are not readily available at big-box hardware stores. Plan ahead and get a bunch now – you will be glad to have them when you need them.