The Age of Empires remasters were a great sucess, with AoE4 on the way.
CoH and CoH2 have both been extremely successful and SEGA is potentially looking towards CoH3.
Wargame: Red Dragon is very popular and successful. Steel Division 1 and 2 are high quality games that underperformed but are still quality games.
Total War has hit a gold mine with the fantasy titles and the introduction of hero units, magic and large units which gave depth to the gameplay and has revived the series.
Hearts of Iron IV and EU4 are grand strategy titles but in essence are cousins of the RTS genre and have been quite successful despite Paradox’s incompetence.
Halo Wars 2 was a very good RTS which got robbed of popularity by Microsoft’s stupid DLC policy. Maybe now on xbox game pass it’ll see more life, especially with the huge hit that is the Master Chief Collection. If M$ are smart they’ll bundle them, HW2 ultimate and MCC for like 40 $.
Starcraft 2 is still a giant of the RTS genre.
Overall things aren’t so bad. I think the main issue for the RTS market has been DoW3’s failure due to Lelic. Had that been a moderate success people would be feeling a lot different.
Strategy games includes different types of games. RTS, RTT, Mobas, Artillery, Turn based, Tower defense, Auto battlers, etc. When we talk about RTS, this leave titles out like the Total War franchise, Wargame type of games or mostly RTT (real time tactics) out of the bag (Men of War, Steel Division).
We are not discussing the popularity of the strategy genre, but the RTS one.
Total War and Paradox titles are a niche genre with a smaller but solid market. Same with grand wargames type of games such as Steel Division/Red Dragon/Men Of War
So focusing back into RTS:
-AoE 2 HD was a failure, not sale wise, but in the multiplayer aspect. Plenty of issues with Steam and people just stayed on the old version of the game and playing through Voobly.
-AoE DE and 2 DE are different beast. Looking great but it's mostly moving the playerbase from the old version to the new one.
-Starcraft is the only last bastion of REALLY POPULAR RTS. I've just checked and it seems theres around 300K 1v1 RANKED players at the moment worldwide. CoH (summing all factions) have around 12K players ranked 1v1 at the moment. And that's with duplicated people (because most people play more than 1 faction). Even if we account team games (as they are more popular) we are not even close.
IIRC 1v1 should be around a third or barely scratching less than half (if we account ALL ranked) their playerbase. CooP is more popular than ranked for example.
That been said, you can ask ANYONE on SC2 and they will tell you (jokingly or not) that the game is "dead". At least, Blizzard didn't know how to capitalise the game e-sport wise, during the launch of Wings of Liberty and "killing" it during the Swarm.
DoW was just one more failure in the list of RTS failures of the last 7 years. It wouldn't move the needle.