The strongest boygroups right now are NCT, Stray Kids, SEVENTEEN, ZEROBASONE and ATEEZ
But since they didn't blew up to the level where even your grandma would know them, like BTS did, people of course do not even talk about them that much. The thing is most likly, because of the fact that BTS blew up so much, people tend to view them like either you like or hate them if you know them. You can ask 100 people on the streets of all ages and I bet most know them or heard of them and more than half of them dosn't cares or hates them, but ask these who like them, they most likly didn't even bothered to check out other KPop for many reasons. Maybe they want to be 1 group only stans, maybe they suck in researching or do not even think they can research to find more KPop, maybe they heard more KPop and don't like it as much as they do like BTS, who knows. It's like Hello Kitty, everyone knows and loves her but most people don't care about other Sanrio-characters or don't even know who the other characters even are. Or like Pokemon, everyone knows and loves Pikachu, but nah, you won't find that many people who know most of the other pokemon and like them more than Pikachu.
People often also tend to stick to what they know and do not even try to test something else. It's like these people who allways order the same food in the restaurant or only drink the same stuff without testing the rest just cause they do not feel bothered to even try.
And since it's Korea, a country that most people do not even live in, that people barly know, a language they don't even speak, it will most likly also be weird and cringe and akward to many people if they would even try to get into KPop other than maybe knowing a few BTS-things. And many people do also tend to only go with whats popular so most likly they also do not want to check out other music cause "oh no, what will people say if I listen to an artist that has almost no fans?" and "since my friend likes BTS too, I only focus on them so we can fangirl over them together cause it might be hard if she dosn't knows any other artist if I might try to get into another KPop act" or whatever the reasons are that people just only care for BTS