Almost certainly toast,
I went thru a long-winded exercise off swapping various used and rebuilt factory reduction starters on my Jeep Cherokee XJ’s.
The short story is they worked perfectly when removed and tested under no load, but failed completely when installed. I proved almost conclusively this was due to failure of the solenoid to pass full current…(they would work in situ if all 3 terminals bridged with ring spanner)
As above answer, they can be dismantled and brushes checked and replaced.
When I did this with one of my spares, which was “rebuilt”,
I found the rebuilder had used inferior brushes, and one of the brush retaining springs had snapped, rendering that faulty as well, swapped factory spring out of dud
did about 4 or 5 SM swaps and dismantles over that little episode
Good news is I had all needed spares, all going now, and a SM R&R on a lifted Jeep is a snack, not so much on stock height