I am not the developer, I just work here on the forums answering questions, but I do know a lot about ACF.
There are a lot, and I mean A LOT, of developers like me that will avoid moving to gutenbug. The reason for this is that my clients do not want be able to edit how content looks on the site. All of my clients are larger companies where every page must look like every other page, every paragraph must look like every other paragraph. If they add an image gallery then every gallery must look and work identically. Most of the time those that are adding the content are not the site owners but people that my clients hire to do the content adding and they do not want or need these people to have any ability to alter the look and feel of anything. I also do not use classic editor even for simple page content. My feeling here is that ACF will always include a WYSIWYG field and this it what my clients want to use. All of my clients are used to using Word Processors and this is how they want to edit pages.
I do not foresee either the flex field or the WYSIWYG field going anywhere any time in the near future.
But like I said, I’m not the developer, just the guy that works this forum. To get an answer from the developer you’d need to contact him, he does not spend a lot of time on this forum, that’s why I’m here so that he can concentrate on fixing and improving ACF. You can try contacting him here https://www.advancedcustomfields.com/contact/
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