Wizard of Oz is a good example. By today's standards of course the production is totally B class, the sets and effects are sub-par and not very good.
I think it's wrong to judge older movies "by today's standards." Films are defenseless against that and today's standards (and exactly what are they?) quickly date as well. All movies are things of their time.
By the way, CHINATOWN is an excellent film. Blame something seeming overrated on those that do the overrating.
Just what are todays standards in movies? Plots that don't make any sense, photography that by the time it gets a digital projection is a murky mess, unmemorable music scores, & really over-edited, so many films are cut like some demented pop promo...but great CGI! There are some new movies I like, but I think most of 'em would come off second best when put up against older movies.