TL;DR Replace Stuff has not been replaced by 1.6.

Honestly, the 1.6 update for stuff replacement is a minimal feature. It merely allows you place blueprints over other things - nothing more. One person deconstructs, then later, another brings materials to construct. Replace Stuff was made to make that cleaner: It replaces in one step, in-place, so it doesn't break your freezer walls / defenses. And since then, Replace Stuff has gotten a dozen more QoL features that 1.6 doesn't do.

1.6 doesn't keep your building settings (e.g. bed assignment). It doesn't upgrade fueled to electric workbenches. Heck, it doesn't handle changing the material of a workbench. When something is auto-rebuilt after being destroyed, Replace Stuff remembers the settings and workbills when it's re-built. 1.6 doesn't handle placing blueprints over rocks or water either, another huge QoL feature from Replace Stuff.

1.6 replacing mostly applies to walls. Also, beds and chairs.. not even tables? Why would there be a special case for chairs but not tables?

The real kicker is: the one bug from last year (that I thought I fixed) where replacing walls removed the new 1.5 wall lights -- well that also happens in 1.6 replacement.

* There was a mod from 2016, JTReplaceWalls, that Replace Stuff was made to improve. That old mod is what this update is, but not actually, because even that let you replace rock walls and 1.6 doesn't do that.