I think you've made the right call, sounds to me like this bike shop guy was fishing for a sale.

Chains are wear items, it is not surprising one would need to be replaced if you rode a bike regularly since 2011. Cassettes and chainrings are as well, but they don't go as fast as chains, it doesn't make sense that they would suddenly all need to be replaced at once.

"he said they are sloppy and will start to skip gears and such" -- do you find them to be sloppy, or do they shift OK for you? Are they skipping gears now, or will they start skipping gears in the future? And yes, cables need to be replaced (or at least drip a few drops of lube in) every year or two or shifting gets sticky -- that doesn't mean shifters are bad. Also, are you experiencing this vibration in the fork from the supposedly trashed front hub?

At best, this is a high-end cyclist who is projecting his refined racing sensibilities onto you and your (presumably more utilitarian), at worst this is a salesman pressuring you into buying a bike even though you have a perfectly fine one.

My best advice: spend an hour watching youtube videos about bike maintenance; you'll see how easy it is, and armed with this knowledge, you can free yourself from the tyranny of bike snobs. Replacing a chain and cables and housing and even shifters if you want, can all be done with non-specialized tools (allen wrenches, screwdrivers, although if the chain doesn't have a quicklink you might need a chainbreaker). Servicing a front hub does require cone wrenches, and skill, but a new wheel can be had for probably $50 -- if you even really need it.