There's a quite a number of WP theme / plugin vendors (again paid not free) and site builders that put off even getting started with Gutenberg until the 1st WP 5.x beta. That was a mistake IMO. Everyone gets busy but that's no reason to flat out ignore and put off the inevitable. It's now been many years since the phrase "Learn JavaScript Deeply" was uttered and nearly two years since Gutenberg development began.

I can imagine that many ( but certainly not all ) need more time because they've already failed to keep up with the pace of their industry. Despite the valid number of issues still in Gutenberg, it seems to me that the v5 release likely could have been that much better off if they'd submitted their issues earlier. Even a year more may not make an appreciable difference as it would just allow them to procrastinate longer probably.

With the classic editor plugin available and potentially even being bundled with upgrades, there should be no issues on existing sites for those that aren't ready yet. The WP Community has seemingly held their breath waiting for Gutenberg and WP to drop and now it's time to exhale.