Struggling with pitch deck "I will not promote"

So I'm still at the pre-seed stage and geering up to start reaching out to investors and VC firms. But I feel like I've kind of shot myself in the foot. I've built up this entire business model that that targets 3 different markets but they all work together to derisk, give credibility and fund the main one. It's a deep tech / civic tech venture focused on media research. And I've worked out all the details for the flagship IP the way the other parts of the business are supposed to function and feed into that one. But now it feels far too detailed to fit into a pitch deck that's supposed to be 12 slides and 20 words per slide. Should I make the 12 slides and have an accompanying document on the ready if they ask for more detail? How long should that document be? Because I had a family member review my initial business plan he says the idea is genuinely great and profitable but you get lost in the excessive detail (it was 50 pages, I know lol). So now I have to take those 50 pages of work that I did over the summer and condense it into 12 slides but in struggling really hard. Like I feel like my idea isn't getting across. Any advice? I could really use any and all help.