As you may or may not know, I look at pitch decks daily. Therefore, I have the advantage of seeing themes.  Outside of the usual issues (for example, lack of a clear problem and solution), here are the top 5 glaring gaps I see that most founders consider way too late:

1. Market Size is Top Down Only

Most founders only use a top-down market analysis without considering the bottom-up and value-theory methods. I ignore top-down market slides. Go Google it, and know that investors expect you to actually ANALYZE the market rather than cut and paste a number from a report online. Don't be lazy.

2. The Business Model is Unclear

Just saying you're "freemium" or "membership"-based is not enough. Investors want details on how you plan to make money and how much. Your pricing assumptions better be battle-tested with customers.

3. Generic Go-To-Market Strategy

Anybody can make a laundry list of marketing tactics. But a strategy is a whole other thing. Don't tell investors you plan to use SEO or "go viral." Explain your ICP, beachhead, and why you assume it will work (real data is best).

4. You Don't Understand Your Competition

If you don't know your competition, investors cannot trust you. There's direct and indirect competition, which includes what users do if they don't have a solution. But there's also every other startup that's building something right now.

5. TRACTION, TRACTION, TRACTION

A traction slide is NOT telling investors WHY you think you will succeed. It is HOW you are succeeding already. Show them clear milestones and inflection points with DATA. And while you're there, break down the data to week-over-week or month-over-month to show growth!

We're here to help with all of the above! Check out our courses on funding, pitch decks, and more here:  https://www.startups.com/courses