I work in financial services administration (in pensions in the UK) and have been with 1 employer for nearly 11 years. I've got another job offer and handed in my notice, and will be finishing with my employer in March. I'm leaving in short for all the usual reasons, low pay, high workload, understaffing, lack of opportunity for progression. 8 team members, out of what needs to be a team of 12, including me have resigned in 10 months, so things are clearly not all well and changes are needed.
The thing is, I've not really gone in to great detail or elaborated on these reasons I'm leaving, beyond the baseline of what I've written here, and I do kind of want to, having only had 2 short conversations with 2 members of the HR team. I want to force accountability for the issues that have led to why I and others are leaving, which are complex, as well as enable others to make informed decisions, and I am presuming that my other colleagues who have left have raised similar issues. At the same time, do I really owe the business any further explanation? I'm concerned that any further feedback I do provide will fall on deaf ears and that things won't change or improve for the members of staff that remain, or for any new team members that join, so I'd be wasting my time and emotional bandwidth providing it. I'm also keen not to be seen to be taking ownership for issues that have arisen by drawing further attention to them, they are not my problem at the end of the day and I need to protect myself mentally and set boundaries, and switch off my ability to care, as I do far more than I should and am paid to. 8 resignations in a team in a short period of time speaks for itself after all, and I also have some healing to do from what I've been through mentally with this job, and I'm not sure how to go about this either. Given I'm starting a new job soon, there won't be much time for recuperation or downtime between both roles.
In short: tl/dr: What do I owe to an employer of almost 11 years, by way of explanation for why I'm leaving the job?