Making decisions with too much data is just as difficult and risky as making a decision with too little data.
There are ways to be logical and move forward in either case.
With too little data, you may want to step back and list or mind map the missing pieces. Which of them are critical, which, if known, would lead to very different answers, which can be discovered before moving on, and which would have little impact and are not worth pursuing. Then you can seek out or make estimates on the missing data noting, as you move forward, what needs a comment or footnote.
With too much data, again you may want to organize what you have into categories, perhaps with sticky notes you can cluster on a board or on a mind map. It’s important to be able to see the big picture all at one time. Then you can highlight, circle or bring to the forefront, the groups that will impact results the most. The others can go on an imaginary parking lot or into the background so you can focus on the most important without distractions.
In neither case, too much or too little data, do you want to feel so stuck that nothing happens. Doing nothing is a decision, too, but one that happens to you instead of by you.