The key, as you said, is proper collimation plus proper cooling and in my case some better focusing mechanisms.
I would add, however, that it assumes a correctly assembled SCT with coincident mechanical and optical axes. I resolved opto-mechanical alignment of an 8" SCT, misassembled at the Meade plant; rear cell installed tilted and then epoxied in place, and therefore baffle tube at a large angle to the optical axis, and an eccentrically glued secondary to boot (!), that was utterly useless, and am finishing my C11, disassembled and rotationally misaligned by the original (and nondisclosing) owner. It appears the rotational clocking of SCT optics is more (or entirely) to get the optics and mechanics totally coincident, and not to offset any errors. The difference in a realigned, formerly soft or unsharp, SCT
Is massive. Not kidding. And I still am refining my 'repair' procedure.
I think maks, with their unitized corrector and secondary, permanently perfectly concentric, enjoy a great reputation, in PART, to eliminating the corrector/plastic secondary housing in an oversized perforation/secondary puck/secondary mirror/primary alignment issue.
Celestron addressed some of these issues in the Edge HD redesign, more noticable if you are reading the white paper with those problems in mind.
'Soft' SCT? It might be the optics, but I believe the aforesaid issues are, generally, more likely to be at fault, and resolvable. Almost certainly.
Unless you have a Halley's Comet rush job with zones, or one of those darn rough corrector Dynamaxes or B&L SCTs!