I think I can.
In terms of advertising, we also have to count stuff like TV shows/specials in with your typical commercials and stuff. Currently two original LEGO ip have TV shows. NinjaGo, which is now on its 11th season, and now LEGO City Adventures or whatever it's called on Nick. Who knows how long that will stick around, but its worth mentioning. Their licensed themes typically don't get a show or special to help advertise the line because it's based off a preexisting IP and therefore doesn't actually need the extra marketing push. Kids will see a Harry Potter set on shelves and think "ohhh, a LEGO toy of that movie I love!" and will buy the toy without a second thought. The IP does most of the marketing for it.
LEGO Star Wars gets the occasional special and short run series (Season 3 of Freemaker Adventures when?) just because it's Star Wars. There's so much room in that universe to play around in, especially when you add the quirkiness of LEGO on top of it, that it'd be impossible not to. DC Super Heroes has a few direct to DVD movies, but it seems like DC themselves might be funding and pushing for those because they're an extra product to sell rather than LEGO budgeting those as extra marketing. And then there's, what, one LEGO MARVEL special that came out around Age of Ultron? MARVEL toys especially market themselves thanks to the IP.
Comparative to these examples, LEGO spends way more time and effort on their own stuff because it's their own stuff. Star Wars and Batman are nice cushions to fall back on in terms of revenue, but there's a reason sets like Creator, City, and NinjaGo were the best sellers in the last couple quarters. The reason NinjaGo is so successful is because of the TV show. Just like how BIONICLE was popular in part because of the comics/books/movies. Up until recently, NinjaGo sets weren't all that impressive, but the theme survived because of the show and how successful it was. Despite continuously dropping ratings (which is at the fault of Cartoon Network), LEGO keeps producing the show in conjunction with the toyline and (usually) put lots of care and thought into the story. Kids respect this and buy the toys to play with their favorite characters.
If we're going to exclude things like TV shows and movies from the talk of marketing budgets, then comparatively, sure, licensed themes do take up more advertisements, but that's more down to contractual obligations rather than no love for their own stuff. As much as LEGO Star Wars tends to market itself based on name alone, you still have to put TV commercials out for it because you gotta tell your audience that new toys are on shelves so Disney can get their cut of the licensing fee. It's also hard to market some themes in today's age. How do you do a commercial for LEGO Creator? Yeah, kind of hard. They're either random build sets like animals or vehicles or it's modular buildings. The audience for these sets don't necessarily need to be advertised toward, and obviously it works because Creator is still here and has been since I can remember.
Let's also remember that time spent on ads doesn't always equate to what sells the most either. In 2018, four of the five best selling themes were original themes and only one licensed.
So I'm not sure why you think that. Obviously they give us lots of original stuff.
I think this is 100% it. Chima wasn't received well, Nexo Knights sorta petered out with little fanfare, and G2 was G2. While all of these LEGO doesn't count as failures, they were nowhere near the level of success as NinjaGo. Why bother competing with yourself? Instead of creating more story themes that end after three years or less, add story to your evergreen stuff. That seems like it's what they're doing with City and it's new show.
And in all of this, I'm pretty sure Friends has some sort of media that I've completely forgotten about since I'm not target demo. So now that's three story based original IP from LEGO to go with their licensed stuff.