According to combat designer Noel Chamberlain who is working on Suicide Squad Kill The Justice League, there is a soft cap on the skills you can earn during the game's story. However, you can earn more skills during the end-game content.
Still, whatever you do it won't be enough to unlock all skills in Suicide Squad Kill The Justice League. Noel Chamberlain made the revelation during an interview with Famitsu Magazine:
"You cannot unlock all the skills. You can obtain skill points every time you level up, but that alone will stop at a soft cap. You can get more skill points from end-game content after clearing the story, but it's not enough to unlock all the skills."
The grind in WB games is getting worse. Gotham Knights had a similar problem but this time it's worse.
Translated by: https://respawnfirst.com/suicide-squad-kill-the-justice-league-you-cant-unlock-all-skills/
OG interview: https://www.famitsu.com/news/202401/12330796.html