In my opinion he keeps selecting him due to not wanting to cause anymore drama/distractions. First it was Ronaldo, then it was Sancho, and on top of that if we there's also the Rashford drama, then it will cause further instability in the team.
And with the team missing key players throughout the season, through injury, it's actually sensible to work around with what you have, rather than enforce a playstyle which the current set of players are either unable to implement or in Rashford's case he can't be bothered to apply the press in coordination with his team mates.
Solskjaer just recently was quoted as saying that he never quite knew what kind of team was going to go out on the pitch when he was the manager. And imo he was specifically talking about players within the team who couldn't be bothered to turn up to play on certain occasions. He praised some players for their effort and commitment but it's not hard to see who he was talking about with his comments.
The culture of a football club begins with the ownership who then employ people to enforce that culture. But if the owners themselves only care about making money, then the culture will deteriorate. And that's exactly what's happened in this case, and maybe Ratcliffe can make a difference in that regard.
For me I'd sell Rashford, our game has to be centred around what each player does on the ball but also what he does off the ball. And Rashford's game on the ball play isn't anywhere near good enough to make up for his lack of effort and desire out of possession. When we buy players to come into our dressing room, it's important to have senior players present that lead from the front and not hide from the front. It sets a example to follow.
Some of us put more effort into our posts on the forum than Rashford does attempting to win the ball back.