Every caliper or V-Brake bike I have ever touched had fully functional brakes. Even if the pads were completely run down and steel was rubbing against the aluminum rim, if you applied enough pressure to the brake lever, you could easily lock up the front wheel.
I bought a gravel bike last year with horrible cable disk brakes and brought them to my bike mechanic. He replaced the clamping unit thing, which improved the braking but was still magnitudes worse than the worst V-Brake or caliper I've ever used. And I'm telling you, I've pulled completely rusted, damaged mountain bikes out of rivers that did a better job braking after a bit of fixing. It is impossible to lock up the front wheel on the gravel bike.
Now I got myself an Oolter Torm S e-bike just this week with brakes even worse than the original ones on the gravel bike. The front brake would somewhat slow the bike down in the beginning, but now, after 90km, they literally don't work anymore. I can pull the lever with maximum force and going downhill a 7% gradient, my speed does not decrease. The disc has blued, which signifies temperatures above 300C, and after pulling the brake with maximum force, the brake pad actually sticks to the disc and wont loosen until you reach and push down on this thing:
I'm better off sitting on the top tube and braking with my feet than pulling the brake level on both these bikes.
Both of my mechanics said they can install hydraulic disc brakes on my gravel bike, but they will need to replace everything, including the lever, which will cost me upwards of 500$ (on a 650$ bike). He said if I'm not willing to switch to hydraulic brakes, I will have to live with what I've got as there is no way to improve them. And there is no way to attach rim brake on the gravel bike fork. I feel like I'm being cheated.
I don't get it. The cheapest, crappiest V brakes will send you over the handlebars if you apply enough pressure, but here I am with disc brakes squeezing the lever with everything I've got.
I've got 2 bikes with brakes that don't work and both my mechanics say "Cable disc brakes are like this". Because of this I was actually tempted to ask "Do cable disc brakes actually work" lol.