You can re-skin monsters and put an encounter together rather quickly in 4e. The problem is that you end up with a rather generic encounter that isn't much different than all the others.
Not remotely true. For instance, the first time I ran 4e was off the cuff at in open gaming at a convention. I'd had an idea for a scenario - a 4-encounter elemental-themed mini-dungeon - and I had some characters' I'd built for the con. When the opportunity presented, I went through the MM and picked & reskinned some monsters, since there weren't elementals of the right level. Specters became air elementals, a black dragon a water elemental, kruthik earth elementals, and fire bats. So, Lurker battle, Skirmisher battle, Solo battle, and Elite + minion - each quite different. Prep time was minutes, result was awesome.
And, before you go "but every battle with standard lurkers is the same as every other..." consider that there were 6 roles, 5 secondary roles, and the leader option - there were essentially 60 broad classifications of monsters. Then you could mix them (even mix solos with others with a large enough party), each combination giving you a different sort of encounter. And, that's if you assume that two monsters having the same roles made them the same, which is also a false assumption...
If you truly wanted to do things correctly in 4e you had to spend much more time designing the grid, including hazards, traps, skill challenges during combat etc.
There's no such thing as 'correctly' there's what works for your group. The DMG had bunches of traps & hazards, the MMs plenty of monsters, if you wanted to combine them, you could. SCs were wonky at first but weaving one into a combat could be worth it. None of that really took oodles of time, though. I've designed epic-level sessions in 20 minutes, a 16th level half-day convention game in an hour and a half. It was just stunningly fast and easy to prep 4e, even with the balky off-line tools.
That takes time, and it takes even more time to add in custom monsters. Heck just knowing what damage dice to use for each type of attack was a royal pain.
It's always been an undertaking to design a monster. Formulae at least gave you somewhere to start, and even when the tools sucked, they made that part easy.
In some ways 5e has greatly simplified the creation of custom monsters
In some ways, in others, not so much. And the encounter guidelines are baroque and less than dependable. I find it's once again easier not to prep at all. Not so much because the prep work is more time-consuming than 4e, though it is, but because there's no payoff. I'll end up tweaking everything on the fly, anyway.
That's not really a criticism, either, I'm very comfortable running that way, it suits my style.
When I say Theater of the Mind I don´t need mechanics that support it. I just need no rules in the PHB that make heavy use of the grid.
So it's not that you want rules that make TotM easier, it's just that you want rules for minis to be inadequate? That's a little weird. What's wrong with supporting both? 13A seemed to do it, and 5e supports mini/grid use in an optional module. It could have had a TotM module, too.
And a 5ft step or shifting also made the narrative worse, since many combats worked as "I run to the archer that he can´t shoot." -> Archer makes a 5ft step back and shoots without penalty.
Nod. The 5' step and the full attack rules could make 3e combats a little weird. Ranged/casting not so much moving as shuffling around, and melee notoriously 'static.' You could buy your way out of it with Spring Attack/Ride-by Attack/Shot on the Run/Mounted Archery on the fighter side, maxxed tumble with Rogues, and maxxed Concentration on the caster side.
4e addressed both issues with more dynamic movement rules contrasted with defender 'stickiness,' FWLIWW.
5e is back to the old 'parting shot' rules, and you can just cast right in someone's face with no issue - but, archers do get disadvantage in melee...
