The sequelitis of the '10s to '50s makes today's sequelitis PALE in comparison.
You really have no clue just how many "Son of...", "...meets...", "Return of...", "House of...", and upteenth-sequel franchises there were. The Mummy's Hand, The Mummy's Tomb, The Mummy's Ghost, The Mummy's Curse, Frankenstein meets Wolfman, The Bride of Frankenstein, Son of Dracula... Getting the point? Béla Lugosi spent most of the rest of his life stuck in that Dracula costume--and then ended up with Ed Wood, that bastion of originality. ::snicker::
Let's put it this way... There have been at least 2 remakes of Freaks, the most unremakeable film ever. Though they bare very little in common with the original. And Freaks already was based on a short story and meant to be a Lon Chaney, Sr./Harry Earles circus freak horror film reunion (not Browning's first). Speaking of which, Lon Chaney, Sr. and Harry Earles even reprised their roles in a talkie remake of The Unholy Three (1925 and 1930). Look at how many times Harry Earles (best known as one of the Lollipop Guild Munchkins) played a baby or a midget pretending to be a baby (most of his career).

I actually wonder if Baby Herman (Roger Rabbit) was inspired by Harry Earles with the cigar-smoking baby gag.
Remaking silent films into talkies was mined for all its worth at the beginning of the talkies period. Often, they even brought back the same cast!
How about the amazing journey of Little Shop of Horrors from cheap horror schlock filmed in 2 days, to musical parody, back to film of said musical parody? LOL. Ditto with Hairspray.
Did you know that an English version and a Spanish version of Dracula were shot at the same time on the same set? That was apparently common practice in the '30s. They reused sets like crazy. Low-budget films were more prevalent then than they are now and sets, costumes, etc... from bigger pictures would find their way into them. I mean, when was the last time a film that actually gets seen was made in 2 days (and has Jack Nicholson, nonetheless)?
The amount of films produced each year has fallen dramatically. People were literally pumping out multiple parts in a franchise released within the same year!
Judy Garland romanced Mickey Rooney in 8 films alone. And that's on top of the 16 Andy Hardy films (I've seen several). Even Boys Town, a legendary Oscar-winning drama, had a sequel (Men of Boys Town).
Taken a look at Shirley Temple's filmography lately? LOL. Formula! Interchangeable! Add Elvis Presley, Frankie Avalon & Annette Funicello, Marilyn Monroe, Jayne Mansfield, Mickey Rooney & Judy Garland, Jack Lemmon & Walter Matthau, Laurel & Hardy, Charlie Chaplin, Abbot & Costello, etc... Those days were the height of formula.
Did you know that Lucille Ball and Desi Arnaz met while filming a formulaic teen flick? It was a college kids movie! And Desi was there to pimp his conga drum act that was a dance craze in the 1940s. The film isn't a far cry from Frankie & Annette. Neither are the Mickey & Judy films ("Let's put on a show!").
Look at how many times Kevin Corcoran did films with Tommy Kirk (5 films--offhand: The Swiss Family Robinson, Old Yeller and Babes in Toyland). Many of those were as Kirk's little brother.
It was more prominent THEN than it is now. People would really be laughing if today's stars were doing 8 films beside the same romantic interest. You can get away with a series or maybe 2 or 3... But not like they used to. Shelley Fabares was in 3 Elvis films. Teri Garr (yes, that Teri "roll in ze hay" Garr) was a dancer in 7 Elvis films.
Babes in Toyland wasn't the first Babes in Toyland (a.k.a. March of the Wooden Soldiers). Alice in Wonderland wasn't the first Alice in Wonderland (in fact, the 1931 film pretty much informed much of what became costume design trial and error for Babes in Toyland and The Wizard of Oz--not to mention Charlotte Henry being both Alice and Little Bo Peep). And not to mention that Babes in Toyland (1934)--not only was it a well-known operetta, it was a Laurel & Hardy franchise film! And not only that, they managed to plug the Three Little Pigs and Mickey Mouse!
There are a gazillion Peter Pans out there dating from the silent era. And then there's Hook, Return to Neverland and at least 2 television cartoons.
L. Frank Baum had his own studio to pump out silent Oz films (there were 14 Oz books by him alone with several spin-offs set in the same universe like Queen Zixi of Ix and Dot and Tot in Merryland--and there have been dozens more by other authors and many, many film adaptions).
Mickey Rooney's 2nd longest career in Hollywood (after Milton Berle) is the story of sequelitis, starting in the silent era. And the silent Mickey McGuire shorts that started his career were another company's answer to Our Gang (The Little Rascals). Pretty much a direct rip-off.
Originality has never been Hollywood's strong suit.