It was announced many times via different media GTK 2.x was no longer in development for quite a lot of time including issues in SWT.
In order to fix a major issue with SWT GTK 3.x port which was that the port was started too late, this time we plan to start early and provide early feedback to GTK developers so our needs are taken in account instead of things workarounded late in the game. GTK 2.x support is a real obstacle for this to happen as keeping so many different code paths (with entirely different design even in places) makes it not feasible to start adding GTK 4.x support.
Today, Eclipse PMC agreed that the 4.10/2018-12 release will drop support for GTK 2.x, set the minimum supported GTK version to 3.0 and the process to rewrite some parts in pure GTK 3.x way will be initiated.
If you have any real show-stopper bugs bring them now. The team fixed most of the important bugs and is now fixing some lower priority bugs. Do not wait till it's dropped to report!
And pure individual visual preferences are not important bugs as it's a design choice of SWT to adhere to system defaults so consider this statement too.
Onwards, to even better SWT!
Red Hat Eclipse Team