Where were you during the beta test?

Anyway, the trigger buttons are gone because it was the single most complained about feature in the old version. You couldn’t fire and aim at the same time (which was sort of a problem) nor could you fire both modes simultaneously with one thumb.
I think the thing you’re talking about is the optional tilt controller. It’s described in Help, but it basically turns the player when your finger is resting on it and you tilt the device; swipe up left, center, or right to fire.
Since you are used to the old version, maybe glance through the help screen to get a sense of what the changes are (it explains how to adjust sensitivity, turn off auto re-center, etc.), and give the default controls another chance. Aim by swiping the screen and using the gyro. Tap to shoot (just as you would in Fortnite, et al.) or use 3D Touch. And of course, tap-and-hold to fire automatically.
Now, I do plan to add a few extra buttons in an upcoming revision. Other people have also mentioned the lack of escape key, and I will probably put in some sort of alternate trigger buttons, too.