are they really this bad?
They are not bad. They are just not designed for what you want to do. They are also horrible at hammering nails.
Techcorner and all these you tube guys raved about this scope.
It is a decent low end scope. But what you want to do is not possible even with higher end scopes, this is not what differentiates them.
Am i better off with a older tektronix scope? I can find one locally for about 100-200 usd
It depends, but most likely no. Why do you think old Tek scope would be better here? Modern digital scopes are better in almost all possible practical respects.
I cant use this thing for anything much as far as i can tell. I cant see how it could be this bad?
It is extremely useful for a ton of tasks, but measuring high voltages is not one of them. Scopes in general are not measurement tools, they are for observing waveforms. If this is not what you want to do, then you don't need a scope.
There is also a question of experiment setup. For example, why do you need to measure that 12 V? What do you expect to see here?
As was described, you may want to measure noise on top of 12 V DC. In this case you can measure DC using a multimeter and use AC coupling to measure the noise. In this case you would need way lower V/div setting, resulting in a much higher accuracy. This is where scope is irreplaceable.