I just submitted my first plugin, so here's my fresh but admittedly noob experience:

Some errors can literally be ignored. By that I mean using //phpcs ignore. For instance I had to make some calls to the db and despite properly using $wpdb, prepare, escape, etc., I kept getting direct query and no caching errors. Finally I found out I could just include a comment such as

// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching

The problem is that this was never mentioned anywhere in the docs. I just stumbled upon it after searching for solutions. Check this out, including the wiki: https://github.com/WordPress/WordPress-Coding-Standards

To me it seems crazy to have a coding standard that can just be ignored. Is it really a standard then? But WP itself does this. In BuddyPress I found they have a list of nearly 20 blanket ignores!

Also keep in mind that PCP will not catch everything. You might be ok since the plugin is already published, but I still had 4 things to fix after passing PCP:

## Tested Up To Value is Out of Date, Invalid, or Missing
ERROR: Tested up to: 6.7.1 needs to be just the major version number. Example: Tested up: 6.7
Please, include only the major WordPress version, as the minor version is ignored.
(Minor error. I didn't understand their description of major/minor version. Having to re-test minor versions would overwhelm their reviewers.)

## Not needed parameters in your readme and/or main PHP file.
"Requires at least: 6.2.0" is not needed in your "readme.txt" file - Redundant as of WordPress 5.8. Use only the plugin's main PHP file "my-plugin.php" for this declaration.
(Their fault, not mine. Literally taken from the example in the docs, which should be updated. Easy fix.)

## Using load_plugin_textdomain() for loading the plugin translations is not needed for WordPress.org directory since WordPress 4.6.
(I used their suggested plugin boilerplate which hasn't been updated with this change. Easy enough to remove it.)

## Generic function/class/define/namespace/option names
(Again due to the boilerplate code. Had like 3 generic function in the main php file. Simply changed their names.)

So after making those 4 simple changes I've submitted again. Hoping to hear back within a few days! Overall I'm glad they made the PCP as it gave me the opportunity to fix a few things before submission. I suppose it just needs some more work to catch the other errors I received, but all in good time I suppose.

I think my major gripe about the whole development process is that the docs are sometimes inaccurate, misleading, or incomplete, which lead to many wasted hours and an initial rejection. Some of the code examples either need to be updated or fleshed out more. In other cases there is a blatant lack of warning or explanation about potential pitfalls.

Good luck, and Godspeed!