If you have already consulted the technicians at an Apple Store or Apple Authorised Service Provider (AASP), you will have already received expert analysis of your iPad’s health - and potential repairability. As described, diagnostics indicate that the iPad is beyond redemption.
As such, other than offering virtual “tea and sympathy”, there is really little else to offer in the way of advice or additional steps for recovery. Anything that can be offered here will very likely repeat anything that has already been tried - and will achieve nothing.
While many devices do last for many years, some can and will reach an early demise - for any number of potential reasons.
An out of warranty repair, if possible (this likely being discussed when you visited the Apple Store with your iPad) will typically cost c.60% of the “as new” cost of your iPad when originally purchased. Given this high cost relative to that of purchasing a new iPad - is perhaps unlikely to be an economic proposition.