But even with a £1B+ overall spend the accumulative amortisation figure hasn't risen anywhere near as much as one would easily think.
That is because, rightly or wrongly, the whole squad of the Abramovich era was ditched and we weren't exactly talking about small money signings there either. In the last season of the Abramovich regime the club clocked like £160M a year in amortisations which have now been removed due to all those players being sold. Or rather almost all, as Lukaku and Kepa are still stinking up the place.
After the summer 2023 transfer window, once all the purchases and sales were finalized, the accumulative figure had only risen to somewhere in the region of £180M a year so not a huge increase over the previous year's accounts. The signings made this summer have once again raised that bar by around £25M a year but still it's only around £40-45M more than pre-Clearlake.
Now
if the club can finally rid themselves of Lukaku and Kepa this summer, the overall figure would then go down by almost £30M a year (£19.5M/y for Lukaku and £10M/y for Kepa to be exact) after which the accumulative figure would at most be around 10% more than the 2021/22 season. So despite all the reckless spending and youth hoarding there hasn't been a huge increase in amortisation costs overall unless the club decide to go on a crazy spending spree in the last few weeks of the transfer window, which I definitely wouldn't put past them.
Right now the high amortisation costs still needs to be offset with the infamous pure profit sales, just as player sales were needed during the Abramovich years. If the club fails to make the UCL this season, then more sales will once again be needed next summer and that's where things can get a bit tricky because like you said the academy pipeline is drying up. The club's plan obviously is to start making money from selling some of the youth players signed for the loan army (ie. Hutchinson sale this year) but for that to happen the youth players need to have properly successful loans and because of the loan limits that might not be possible with all of them. Like
@WeePat said it's a grim way to run a football club, but it is what it is and there's not a whole lot us fans can do about it.