Wales winger Bale made just 16 LaLiga appearances, including only 12 starts, and scored twice as Madrid won the title this season, ending Barcelona's recent run of dominance in Spain.
The 31-year-old was fit for much of the campaign but fell out of favour with head coach Zinedine Zidane.
Bale's agent, Jonathan Barnett, insists his client – once the world's most expensive player – is not looking to depart Madrid, yet his prospects of a return to the first XI appear slim.
The former Tottenham Hotspur player almost left for Chinese Super League side Jiangsu Suning last year, and team-mate Kroos wonders if he is "still a bit mad" the move fell through.
"There's no getting around it. The situation is unsatisfactory for everyone," Kroos told the Lauschangriff podcast. "He certainly wasn't brought in to play as little as he does now.
"I believe that he wanted to leave last summer in principle and that the club agreed at first and then said no.
"I don't know if he's still a bit mad about that. It's a difficult subject.
"It's certainly not as extreme as is said [in the media]. Everything is okay in the team. I've known him for six years and we've won some pretty big things together."