Ilbranteloth
Explorer
I've never in 35 years of playing, run a "boss' monster without the environment and likely tactics the monster would use be a huge factor. While you might run into a normal room with a couple orcs in it and the battle is pretty vanilla, "boss" monsters always have something else around them to impact that battle. In 5e, many of these have lair actions, but regardless if it's an ability or not, very rarely will a boss be in an environment where they don't know the area extremely well and use that to their advantage.
What this means is that I will have a hard time doing the experiment, because the outcome of these battles is less dependent on edition, and more dependent on how you're DMing them and what sort of environment is there.
Agreed, this is one of the challenges. But I think this is one of the areas that people don't always do, and thus the monster is easier to kill.
On the other hand, running the same encounter without those factors using the same monster and party from different editions would potentially highlight that the lair and legendary actions play a bigger part in the 5th edition.
It's hard to do a direct comparison in any event, because a 1st edition lich didn't have lair actions or legendary actions. But I think we can make some sort of comparison.
Ilbranteloth