While I agree with most of the above, part of the problem is DC really hasn't developed many characters(at least enough to carry their own solo series) that haven't been part of the Justice League.
According to wiki: Here is the current list of active DC titles:
Title Volume Debut Date Notes
Action Comics vol. 1 June 8, 2016[1] Resumed original numbering, commenced in 1938
Aquaman vol. 8 June 22, 2016[2]
Batgirl vol. 5 July 27, 2016[3]
Batman vol. 3 June 15, 2016[4]
Batman/Superman vol. 2 August 14, 2019[5]
Batman and the Outsiders vol. 3 May 8, 2019[6]
Batman Beyond vol. 6 October 26, 2016[7]
Books of Magic vol. 3 October 24, 2018[8]
Catwoman vol. 5 July 4, 2018[9]
Detective Comics vol. 1 June 8, 2016[10] Resumed original numbering, commenced in 1937
Doom Patrol: Weight of the Worlds vol. 1 July 3, 2019[11]
The Dreaming vol. 1 September 5, 2018[12]
The Flash vol. 1 March 4, 2020[13] Resumed original numbering, commenced in 1959
The Green Lantern vol. 1 November 7, 2018[14]
Harley Quinn vol. 3 August 3, 2016[15]
Hawkman vol. 5 June 13, 2018[16]
House of Whispers vol. 1 September 12, 2018[17]
John Constantine: Hellblazer vol. 1 November 27, 2019[18]
Justice League vol. 4 June 6, 2018[19]
Justice League Dark vol. 2 July 25, 2018[20]
Justice League Odyssey vol. 1 July 18, 2018[21]
Legion of Super-Heroes vol. 8 November 6, 2019[22]
Looney Tunes vol. 1 March 3, 1994 current issue: 254
Lucifer vol. 3 October 17, 2018[23]
Mad Magazine vol. 2 April 18, 2018[24]
Nightwing vol. 4 July 27, 2016[25]
Red Hood and the Outlaws vol. 2 August 10, 2016[26]
Scooby-Doo, Where Are You? vol. 1 September 1, 2010[27]
Shazam! vol. 3 November 21, 2018[28]
Suicide Squad vol. 6 December 18, 2019[29]
Supergirl vol. 7 September 7, 2016[30]
Superman vol. 5 July 11, 2018[31]
Teen Titans vol. 6 October 26, 2016[32]
The Terrifics vol. 1 February 28, 2018[33]
Wonder Woman vol. 1 January 22, 2020[34] Resumed original numbering, commenced in 1942
Young Justice vol. 3 January 9, 2019[35]
No way you can make a team out of non-Justice League characters that have current solo titles(and you need something to pull people to the team).
For Marvel, Ghost Rider, etc helped establish the Champions(but didn't last long in the '70s) and then Miles Morales Spider Man and Kamala Khan currently.
Defenders had Hulk, Silver Surfer, Dr. Strange.
You almost have to have a pull(usually a character with enough following to support their own solo) to make an extended run for a "new" super-team.
Hence, Batman with the Outsiders.
Super-boy with the Legion.