Injector clean is a money grab. The other services yeah those are legit although a lot of people don’t do it. I’m a little more conscientious than some and do change coolant, brake, ps, diff fluid at 100k or sooner depending on what it is.
Coolant and diffs are straight forward. I’m not motivated enough to flush bleed brakes or drain power steering, but for a few more bucks and a lot less time, you can suck the reserviours for both out multiple times and capture most all the old fluid.
For ps, can do it with just starting the car for a min between rounds. Brakes, I do it repeatedly with some miles in between to ensure the new fluid mixes thoroughly with the old.
Say you get 50% of the total each time. That’s 50-75-87.5-93.5% after you’ve done it 4 times.
Basically as good as any oil change gets.