when I hit bumps or dips in the road the front of my driver side tire moves left to right extremely fast. Almost like you’re turning left to right as fast as you can.
Interesting problem, but I'm curious what you mean by this. Is that what it "feels like"? Does the steering wheel pull? Was it like this before parts were swapped? or before/after alignment?
It sounds like something is sticking (or loose.. like a shock.. as if the top mounting nut came off) so the front end doesn't move up/down equally on both sides. Is hard to tell if it doesn't move much w/stiff truck springs, but maybe try bouncing up/down while standing on bumper to see if both sides move about the same.
Others have said things that could happen from age/rust. Could be something was damaged while replacing parts (I'd think you'd have noticed) or something got messed up when the shop raised the vehicle.
"Front end slack" is too general of a term. I don't see how anything could have 'slack' after replacing parts. If something was bad/loose, it's a safety issue and they should have been specific - could be they didn't want to do the job and said some BS. The shop manager at a local Midas (which my buddy owned until recently) took customers into the shop and showed/explained anything that was wrong/needed fixing (like why they'd charge for 30 minutes labor to break components loose on my '68 Chevy rustbucket before they could align it - I knew it was a mess and was happy to let them deal with it).