A not-very-good trigger makes tight groups more difficult, but it does not keep one from shooting tight groups. It merely takes more concentration and control.
I have a CMMG flat-top upper with a 20" lightweight barrel on a Colt lower with a reasonably decent trigger. Sub-MOA with a 4X scope. The complete upper was around $600. (Shrug) Tactical isn't of any importance to me, since it ain't looks what kills coyotes and jackrabbits.