This.

No one should take PG's quip to be anything more than advice for those who are running a dysfunctional ship due to excessive obsession with competitors.

There are likely two broad ways any business gets off the ground:

(1) Unintentionally (2) Intentionally

Google was likely unintentional (Brin and Page weren't attempting to create a business for their dissertation).

Amazon was quite clearly intentional.

Most startups are likely in (2).

VC-backed startups and startups hoping to obtain VC funding have a goal of gaining some amount of strong traction (thus increasing the likelihood of fast and significant growth).

If you're intentional, and you have a goal of obtaining the traction that's attractive in the VC universe, then competitive strategy is not something you can ignore. It's not something you myopically focus on, but it will help guide your positioning and development (among other things).

> doesn't it make sense to build a defensible strategy , building things your competitors will find hard to copy ?

How does looking at what your competitors are doing help with building a defensible strategy?

Either you're copying what they've already done and are playing catchup with already exists or you're somehow looking at what they haven't done to implement something you think they'd be hard to implement, in which case you're focusing on what your competitors are not doing instead of where you think will provide the best value to your Customers.

Which I believe is at the heart of what PG is saying, you should have relentless Customer focus and do what you believe delivers the most value instead of focusing on competing against your competitors.