Well Dracula is always popular. I also enjoyed the 2010 Wolfman film fairly well, and of course the '99 Mummy spawned an entire franchise. Van Helsing was also a pretty big hit in 2004, grossing $300 million.
You may be right about some of the lesser monsters like the Invisible Man and the Creature from the Black Lagoon, but the A-listers have always been popular.
The '99 Mummy is one of my favorite films of all time (though I'll agree the sequels are poor). And like I said I also enjoyed The Wolfman fairly well.
Haven't seen Dracula Untold or Van Helsing, but I've heard more good about Van Helsing than bad.
As for The Mummy (2017), I thought it was enjoyable enough to buy it on Blu-Ray. Not a GREAT film, or as good as the '99 film, but a fun and well-made movie that has a lot of excellent visuals.
I'm close to your age, but I like these old monsters because some of the happiest hours of my youth were spent watching "Creature Features" on late night TV.
I always thought that this "Dark Universe" was a good idea for a franchise, because fun, scary, campy, entertaining films could still be made using these old properties. If it hasn't worked, it's because all the movies they made were terrible, which is a pity and isn't the fault of the source material. It's like the DCEU comic franchuse: the basic idea is good, it's the execution that sucks.