All true points about it being difficult to cut straight first go with no prior use of a saw ever.
“Totally straightforward, unless you’re completely clueless and have never held a saw before [like everybody was when they first held a saw]”
It’s certainly harder if if you’ve got a crappy little junior hacksaw with dull blades and a clamping mechanism that pull the blade off at an angle when you tension it up. For example.
A decent hacksaw and blades to match the job isn’t a negligible about of money compared to getting a shop to do it for you, but it’s a purchase that’ll keep on giving. Plus there’s the chance that the guy in the shop is even worse with a saw than you!