P+T are unsurprisingly focusing on Craft CMS, which they created a few years back.
Craft has many similarities with EE and it seems that - at least as far as the online slack community goes - many EE mages are now also working on / with Craft these days.
If others have moved on to other CMSs - in part this must be due to problems associated with the botched launch of EE3. The first releases of EE3 were incomplete and few EE2 addons had EE3 versions available at that time.
This triggered a chicken-egg issue: without an equivalent set of addons migrating EE2 sites to EE3 wasn't really possible, but since the migrations were not taking place, the market for EE3 addons was smaller than before (as presumably EE3 sales were to people doing new builds that - reflecting the lack of addon availability - didn't need many addons) - so after launch addon authors didn't have much incentive to put in the effort / investment into updating either. Some, like P+T despite initially saying they would get around to rewriting EE2 addons for EE3 concluded it wasn't worth doing at all and either abandoned EE2 addons or sold them on to other firms / developers, others just took a very long time to complete the work.
We're now a long way down the track from the EE3 launch now, and things are much better than they were: there are at least some alternatives for all the major EE2 addons around.
EE3 itself is stable and fast, and has a roadmap for development (at least Ellis Labs are beginning to refer to EE4 at least as a concept). However it is hard to know what impact the the lost year and general confusion surrounding the launch of EE3 has done to the long term viability of the CMS.