Reagan was regarded (famously coined by Clark Clifford years later) as an amiable dunce, a lightweight movie actor, "second banana" to a chimp. He briefly flirted with running for President in 1968. His speech at the 1964 convention identified him as dangerously radical, outside the mainstream...even more radical than Barry Goldwater, the target of the infamous 'Daisy' ad.
In 1976, there was no more establishment politician than Jerry Ford. Many believe the RINO Corps a recent phenomenon, the uniparty a modern plague; if the Uniparty were a basketball league, Jerry Ford would have been on the logo, rather than Jerry West. There was near unanimous support for establishment positions such as Keynesian politics and arms control, all wrapped up in the notion of a 'gifted elite' whose job was to govern the rubes. Carter was more of the same, safely establishment and elitist...best of all, "Ah weel not lah to yew."
Reagan, by contrast, was none of these things...not elitist, not Keynesian, not a supporter of arms control as practiced...therefore, intellectually unserious, a dangerous demagogue seeking to con the simpletons.
Reagan was publicly regarded as all these things, most of all by the establishment (including the Repub establishment.) I believe he was right on the issues, which goes beyond 'intellectual' as currently practiced. He was settled in his views. This is the only difference I see with Trump.
I'm guessing you have a few rings around your trunk...you must surely know this.
What Clark Clifford (a partisan Democrat) said about Ronald Reagan is relevant in what way to what partisan Republicans are saying about the Donald?