" Before I test anything I always try to work out what I really need from it, not what I would like but what core functions does it have to be able to fulfil without friction."
From experience (I’ve been trying out task-management apps since more or less they were invented for the Mac, at least), I can only underline the importance of what TheOD has written above.
Write down the task-management functions that you really want and need, and only afterwards look at the choices of applications on offer. Then evaluate the choices against your feature “must-have” list.
An example: for many years a number of task-management apps lacked start or “defer” dates, but didn’t shout about it. Only a few (including OmniFocus) had them, but also didn’t always shout about it. Reading forums like this one, it was obvious that a number of users of the apps that lacked them fudged how they used them in order to make up for the lack - or complained loudly about it. In fact, it became obvious that some task-management apps were quite unsuitable for the uses that some users wanted to put them to, whilst other users were perfectly happy with them. If users tended to work on “quick-turnaround” tasks, they tended not to require start or defer dates and in fact sometimes found them an unnecessary complexity; others like me, whose tasks can run for days, were pretty much lost without them.
So to an extent not necessarily immediately obvious, the right task-management app for you depends not just on, say, its dark-mode functionality or similar qualities, but fundamentally on the type of work that you do and how you do it. And when it comes to task-management apps, there remain some often quite surprising differences that aren’t necessarily immediately evident but which can make some of them much more suitable than others for your style of working. So - as TheOD says - list, test and evaluate.