If they want to draw in the younger crowd, they're really going to need to start pushing horror video games, shows, and celebrities into houses. Draw in the fandoms that intermingle with the horror fandom. Eilish would have been great for this before her image change but there are still dozens of fandoms that are primarily made of younger people for games, shows, and artists that have horror aspects. Bendy and the Ink Machine would have done well in 2018, Five Nights at Freddy's will still kill it, Welcome to Nightvale would have been great in 2016, etc. I mean, just look at how well American Horror Story and Stranger Things did. In other words, to draw in the younger audience they were trying to target with Eilish, they need to look at the fandoms of Tumblr, Twitter, and TikTok and see what's blowing up. They're not going to get the same effect with either Creepshow or Halloween.
Best chance they've got right now is hoping that some hype from the Beetlejuice Musical (another fandom that has a ton of younger people) is going to transfer over into excitement for the house, which is likely considering the rumours of the musical's return. But I honestly feel like if Universal goes forward with either Creepshow or H3 for the Eilish replacement, they're going to be missing out on drawing in the younger crowd to the same extent they did in the past 4 years.