I do not claim great expertise, but here are my thoughts.
You didn’t mention air. How is the filter? Try starting it without the filter.
If you have gas, spark, compression, timing and air, then it must start. So, something doesn’t compute and you have to go back and reevaluate your conclusions.
Could the shutoff wire that grounds the coil be shorting out? (Is the switch in the run position?) I would disconnect the wire at the coil and see if that solves it. If not, then I’d shoot some starting fluid into the cylinder and see if it fires. If it does, you have a fuel problem. How fresh is your gas? I heard you say it has compression, but you didn't say you tested it. Someone here gave me this great advice, remove the plug and put your thumb over the hole. Pull the starter cord and you should not be able to keep your thumb on the hole. Valves not working properly can screw up compression. Is the exhaust side obstructed? Does your machine have one of those screens that clog up?
It is possible to have visible spark, but it is weak. You’ve already replaced the plug, so maybe you have a weak ignition coil. Do you have one you can swap from a working machine, like you did with the carb?
I’ll tap out and let actual experts have a go. Good luck.