There is a word for people who only focus on big ideas: crackpots.

The truth that every entrepreneur has to face is that it takes big resources to pursue big ideas, and very few people have big resources at their disposal. Even Elon Musk had to blow up PayPal before he could pursue truly big ideas.

The vast majority of giant corporations come from executing well on a series of progressively larger operational goals. The trick is figuring out how much you can actually bite off successfully at each stage, and then doing it several times in a row and scaling accordingly. The big ideas can come when you have the money and the influence to execute on them.