The first is skipping it. "We're building something new, there's no real competition." Then they launch and find out the space has three established players and a pricing war already in progress.
The second is doing it constantly but superficially. Checking competitor homepages, following their LinkedIn, noticing every rebrand. You end up knowing a lot about their marketing and nothing about their customers.
The version that actually helps is narrower than people think. You need three things: what they charge, where their customers are unhappy, and which channels they're ignoring. That's the information that tells you how to position, who to reach out to first, and where there's space to grow.
Everything else is noise.