Nicely put, I've always felt this. As an example, playing Age of Empires much of the early game is fast resource grinding and scouting, all manageable. But when lategame hits and you start moving armies, so much mechanics and microgame comes to play while the macro and strategy still stands. While you have to kite with several armies at once versus a skilled opponent in a sluggish battle, your goldmine might run dry or your farms needs to be rebuilt, you have to use your villagers, research techs and keep recruiting new units. All of this is impossible for my brain, that's why I stick with strategy games like Civ or HoMM, but the thrill of RTS is always fun with friends while turnbased games might become cumbersome.
yea i notice this a lot. its really daunting to micromanage in real-time and most developers understand this and usually add a pause or slowdown button somewhere but that ironically just makes it a turn based game. FTL is a good real-time strategy but the pause button takes the 'real time' out of the experience and turns it into a solely turn based game. it may not feel like it because seconds aren't as abstract as turns but an attack that takes multiple seconds is identical to an attack that takes multiple 'turns'
strategy games can accomplish a lot more mechanically than real time strategies but the side effect is that all the depth usually goes unmanaged and becomes complexity. a lot of strategy games like to have 100 different choices but each of those choices have very little tangible outcome on the next few turns, much like an rpg game with 2000 different weapons has no depth because all of the weapons are just minor stat changes and any one will work. civ and grand strategy are pretty heavy TBS that require a lot of patience, maybe too much, and can really slow down late game when there's a lot of complexity you have to manage and each turn takes like 10% more time than the last one to think through.
ideally the best strategy games are ones where you only have to process up to 7 different choices a turn. that's like the ideal middle ground between depth and complexity, when you have just enough meaningful choices to make educated plays but not too much that you ignore half of them because its not worth the brainpower. 7 is the magic number of how many different abstract objects most people can hold on memory at one time. if you've ever played xcom ew or xcom 2 you'll see this in action once you get a squad size of six. at that point in the game you have so many choices to process (3-4 meaningful abilities per unit, 6 units) that you end up only using like 1-2 of the abilities the entire match or even forgetting to move one of your soldiers / mindlessly moving it into a bad/poorly thought out position because your brain is exhausted
even in real time games you can see the same pattern. if you've ever played rocket league you'll know that there's 3v3 modes and 2v2 modes but 2v2 is more popular. in a rocket league match you have to process the ball and all the players, some of which you can't even see at the time. in 3v3 that's 6 players you have to process at any given time as well as the ball's position and it gets harder when you can't see all your teammates and you have to formulate where they are on the map without looking. people play 2v2 more because there's less things you have to process, which allows you to focus more on the individual objects and leads to better understanding of positioning and ball reading. in 3v3 you need to block out a lot of the processing of players in order to focus on the game which leads to double commits (two players going for the ball at once) or even just forgetting about the timer and realizing once the game has 30 seconds left that you're 2 goals behind
basically all games suffer from the same bottleneck of the player's processing power. the more entities you have to think about the less thought you can dedicate to each entity and the lest meaningful each choice is. a lot of designers now are learning that giving the player more than 6-7 choices at any one time in the game is bad design. we've been blessed with games like into the breach and baba is you which focus more on limited simple mechanics that lead to complex outcomes