of course i understand that maintaining compat layers is very painful but dropping symfony 3.4 support is a very bad idea.
symfony 3.4 is a LTS release. it is supported until nov 2020 and gets security updates until nov 2021.
it was my choice to stick with this version so i can use my time to build new things and not keeping all my projects up to date. i assume that also some companies go for LTS releases, they also want to invest their workers time into new projects instead in keeping all project up to date with the latest framework version.
in the past years the "version rush" gets more and more terrible. i am not a big company, i am a one person company and really struggle to keep everything up to date.
today an update is not "i make a security update and my lib, app, tool, ... is secure again and i can move on", no its you get an update with your necessary secuirity updates AND you get tons of new features and you also loose a lot of features. features you need, featrues you build upon. also many updates breaks things. a lot of people out there even don't use SemVer (or they use SemVer but like google does it for chrome).
i often discuss with user why they don't update ....... (insert software/lib/app/... here) and that it is very important to update,.... but a user only want that the thing works (what it does without update) without much effort, without getting used to the new interface, without searching for the new locations for the functions and menu items. i tell them, that its very important to update... security...
but i can understand them.
Rasmus Lerdorf asking his audience who is using php 5.x (watch at least min 26:08-26:45)
but thats reality.
so please add a BC layer so that we can test our new and old application with your awesome testframework.