It had problems here and there. But you could change the character of the government by voting a new man in. Also you could judge the man by the way his administration performed.
He couldn’t claim policy was beyond his reach.
It also reduced the number of bureaucrats who made government work a lifelong career.
If only Americans of that era could have seen where their reforms would lead, they would have never passed them.
Interestingly enough, the assassination of James Garfield accelerated concerns over the spoils system and may have played a role in heightening calls for reform. As you pointed out, it may not have been perfect but at least problems with bad administration could easily be dealt with by voting in a new president. The spoils system might have lead to corruption, but it was less likely to lead to the generational corruption we see now, which is far worse and harder to eliminate.