While personal opinion matters, your logic is flawed.
First of all, manager of United is not some internship job with those kind of easy going expectation. The minimum requirement is well known: top 4 thus CL qualifying. Moyes failed. LVG earned his second year. Moyes hardly improve with the money at Everton and didn't know how to spend the money at United so if LVG hardly improve by spending money so does Moyes.
Secondly, players are not machine, and management skill is not production skill. Moyes inherited an experienced squad which carried him at times. Moyes was able to piss off Rio & Vida, then Evra left with personal issue leaving LVG with a less inexperienced squad when playing in CL. So. Moyes himself was not really better in CL given human players may play a huge factor.
Thirdly, again, Moyes didn't implement a new style. His style is simply a downgrade version of SAF's style. Players have on and off days due to his inability to manage the team while using a similar style. LVG tried to implement his philosophy and forced players to get accustomed to it. It didn't work, so the style is no where perfected. Still compared no plan/ regressing plan to half done plan, the latter should be viewed as positive.
Last but not least, Moyes is as old as Mourinho even 3 years ago, he shouldn't be considered as potential coach thus he shouldn't get the job under normal circumstances. He is he definition of fraud. LVG failed to live up to his reputation. If you give. Moyes the leeway in learning the top level job, then LVG should ask for the excuse of learning the PL: Over a decade experience vs 2 years...
So all in all, giving Moyes an excuse would be equivalent of giving LVG a different excuse. Thing is LVG accepted his failure and had moved on (thus far). The other one can't still have his head sorted....
One climbing up a slope still went a farther distance from one climbing down from the top... There you go.