You kinda proved that you weren't even trying to role play, , and in the end you had to restart a playthrough because you weren't paying attention.
i played as a renegade but i most definitely didn't just restrict myself to renegade dialogue. i said what i thought my character would say, sometimes fully knowing i would get paragon points, because i was role playing as the character.
it sounds like the problem was how you approached the system
as for your other points; bad voice acting, too cinematic, i respect your opinion, but disagree.
No, I was paying attention. This happened on my very first play-through, so I was definitely paying attention. That is why I think the hint system svcks. My Shepard was talking to Jacob. Being nice/paragon instead of being a jerk ended up starting a romance that my faithful to Liara Shepard did NOT want. So I restarted and ignored Jacob ever after. You see, when I can see what my pc is going to say I can decide whether I want to pursue this line of conversation or not. I never accidentally romanced Zevran in DA:O, for example. I could see what my character could say before I found my character actually saying it.
I approached the system thinking it would work. I found myself saving before conversations though, after a few of the hints ended up different than what I wanted. I have reloaded to pick a different hint in the hope of getting the dialogue, or close to the dialogue, I wanted.
I never said the dialogue couldn't be mixed. There are times where my paragon switches to paragade; I can't not headbutt the krogan, for instance. Generally picking the upper right reply won't be a bad or jerk reply. Picking the lower response generally won't be the nice reply. I do roleplay. I just like more control over my role-playing than guessing at what I'm going to say.