I don't even remember when I last worked in a non sprints/cycles way (the year started with 201x or even 200x). But sprints does not necessarily equals cycles,

I don't even remember when I last worked in a non sprints/cycles way (the year started with 201x or even 200x). But sprints does not necessarily equals cycles, and cycles does not necessarily equals Scrum or Agile. I totally agree with you stand that "overly ambitious sprint planning" is the root of all evil, many teams forget that planning is not a construction plan but more of a show of intents and you can see the stress level fluctuating between the start and end of sprints. Another big problem is task estimation, we know that we are bad at it but the "process" forces us to estimate anyway. This in turn leads to more of the above mentioned stress since we usually under estimate. I found that many times usually Kanban, or ScrumBan works quite well and mitigate some of the mentioned problems.