This is all very true. CSS Grid does simplify the markup needed for a column based site, and means that people willing to design everything themselves do have a

This is all very true. CSS Grid does simplify the markup needed for a column based site, and means that people willing to design everything themselves do have a better alternative to frameworks like Bootstrap and Foundation. However, I think what a lot of people miss about these frameworks is that they're not just easy to use systems for coding a grid layout. They also provide decent 'default' designs for people with zero artistic talent. And that's crucial for people who struggle with things like colour schemes, button/menu/pagination designs, etc. For someone whose favoured design ascetic is that of a 90s Geocities page, the standard Bootstrap styles will at least help it remain looking like something from the 21st century. Bootstrap isn't just a frameworking tool, it's a quick way for people with no visual design skills or without a proper designer to make something that looks at least passable by using the default components and their included styles.