Overall RTS games pushed the technology to the max in the 1990s but were exposed as mechanically dull and repetitive in the 2000's. MOBA's completely took over the space.
Did they tho? Age of Empires 2 multiplayer survived into the 2010s, then they released a HD Edition in 2014, then they released new expansions for that HD edition, then they released a Definitive Edition which still keeps getting new expansions despite AoE4 being a thing now...
And I still greatly enjoy playing AoE2 myself. It's a thoroughly solid game with great gameplay, not dull at all. Four resources, various factions with small differences in how they play, lots of important decisions that can decide the outcome of the game, macromanagement mixed with micromanagement (deciding what kind of army to build, where to expand your base, etc vs managing your units in battle), a big focus on map control, etc.
MOBAs are fucking banal shit boring. I tried League of Legends when it was popular, and it basically felt like Warcraft 3 without all the fun parts cut out. All you do is micromanage one hero. THAT is mechanically dull and repetitive.
In a game like AoE2, only the Dark Age is repetitive as you go for a standard build order to reach Feudal Age. Once you're there, everything is possible. Bunker up and focus on economy? Go for scouts to raid the enemy woodline, or archers? Stay in Feudal Age a little longer and focus on putting pressure on the enemy, or beeline to Castle Age to get precious knights? All the while you keep scouting the map and assess its geography for potential angles of attack and resource spots to secure.
The HD and DE releases only added more variety to the game by adding a ton of new map templates. Multiplayer maps are randomly generated based on a template. Arabia is the most popular (but I find it kinda lame tbh): an open desert map with few woodlines so it's not easy to wall up, but easy to raid. The opposite of that is Black Forest which has trees everywhere and only few passages that can easily be walled up. Then there's several water maps like islands where you need to build a navy to reach the enemy, completely changing the approach you need to take (and shifting the civ balance in favor of civs that have navy bonuses). Then there's maps like Gold Rush where there's a huge amount of gold in the center of the map, putting a huge importance on map control. Those are all original map types... HD added fun stuff like Socotra, a tiny African island where resources are scarce and the distance between you and the enemy is so small, conflict will start much sooner than usual.
But the best maps are Megarandom and Nomad. Megarandom tosses any regularity out the window and does whatever it wants. Sometimes it spawns more boars around your base for easier access to food, sometimes none at all so you have to farm earlier. Sometimes it gives you a free building at the start, like a stable or a bunch of towers (which make raids more difficult, directly influencing the viable strategies right as the game starts). It forces you to adapt and think beyond standard build orders, and makes scouting even more important because you really don't know what the map looks like until you uncover it.
Nomad on the other hand is a more regular map, but it doesn't give you a town center at the start. Instead, you start only with villagers and additional resources and have to build your TC yourself. That involves initial scouting for a good position, but you shouldn't take too long or you'll waste too much time which you could have spent producing villagers from your newly built TC. You start without a scout and since nobody has a TC at the start, you also have no idea where the enemy will be until you stumble upon their base later on. It can be incredibly chaotic and relies a lot more on rapid decision making based on current circumstances than blind repetition of standard build orders.
AoE2 on Nomad and Megarandom is peak RTS. And it's very, very far from "mechanically dull and repetitive".
