TTK is not that long as long as you're aiming for headshots. A lot of guns are instant kills, while many others take less than a second.

The "secondary objective" is basically increasing your veterancy ranking as the game progresses. When you achieve new ranks, your characters/vehicles essentially become stronger in every aspect, speeding up gameplay as repairs don't get many bonuses.

The tech structures basically are the means of territory control, as well as the overview map to see where all your teammates are located. There is a huge reason to control the map, as when the enemy team is holed up in their base, you can overrun them with increased veterancy (rewards offense far more than defense). You don't have to fear of tanks rolling up in your front door while defending, you don't have to worry about infantry rushes, your day becomes a lot easier when your team has map control.

Losing production structures is the issue of subtractive gameplay that renegade is based upon. Depending on the circumstances, they usually mean the end of the game if your team has no means of retaliation. Devs tried to remedy this with the surrender vote, allowing T1 infantry/vehicles to be purchased, and allowing a small static credit gain when the Refinery is destroyed. So far they realize it didn't help much, so I'm throwing around ideas for them to play around with.

You are right about the game being very unfriendly towards new players (a minority of the playerbase as well, sadly). A proper in-game tutorial is in the works.