How to avoid flat website structure in SEO?

Whenever we start doing SEO for a client, we follow below process

• Audit
• Keyword research
• KW Selection
• Blog post creation
• Service page creation

But recently i came to know this makes website structure a flat/horizontal structure (a marketing guru pointed that)

So main question is how can we save ourself from making this flat structure (Don't suggest blog categories here)
Also do share some examples if you have any

What's wrong with blog category structure? You can use categories in the menu and breadcrumbs while permalink as domain/blogpost.

IM Dude said:

What's wrong with blog category structure? You can use categories in the menu and breadcrumbs while permalink as domain/blogpost.

Click to expand...

Hey, nothing wrong in it, infact i am doing my SEO the same way like xyz.com/blogs/post1...post2 and so on... Question is if you want to expand this silo rather than having horizontal spread, is it advisable to do it? if yes, then how do you suggest we should do it