Scala 3 didn't "drastically" change syntax -- most of the changes also have automatic rewrites with appropriate compiler switches. The effects story is still pretty experimental, but there's also improvements to 'effects' syntax (for-comprehensions) in "preview" for 3.7.

As long as the 'effects' work will let me distinguish pure/non-pure, I'd be happy to use just that bit and stick with ZIO/TypeLevel's ecosystem... which will probably be supported forever, regardless of whatever happens with the "effects" stuff.

Perhaps the focus of the team behind the compiler has changed over the years - but there is still backwards compatibility (via TaSTy), the new syntax changes are not mandatory (for the moment) and when they do become so there will be a fully automatic (and correct) rewrite. There are new libraries exploring "direct style" but you can still use cats-effect or ZIO if you prefer. If anything, Scala has a "too much choice" problem (and kinda a community one).

One of OCaml's outstanding, but too little mentioned, virtues is the community's commitment to extremely strong backwards compatibility guarantees.