If the rest of the computer is old enough, there's probably still a benefit and even if there isn't it's not slowing things down.
I'd say that if the rest of the computer is old enough to slow things down it shouldn't be running Windows 10 in the first place, because I'm unsure if it'd be comfortable to use.
Actually, what would be the minimum system requirements for comfortable everyday usage? Because I'm pretty sure it isn't the minimum requirements listed by Microsoft based off previous experiences with computers on the low end of system requirements.
I've found 10 to be about equal to 8, and slightly lower than 7, actually.
Although hardware configuration matters a lot, and older hardware configs will have serious driver and performance problems. Also some configurations will be significantly better on 7 than 10.