You might say that the subscription model is essentially the same as what I described above: your permanent license will eventually be for a piece of software that doesn't work anymore, and you have to keep paying in order to keep using your tools. This is 100% true, and subscription means you pay a little at a time instead of a lump sum. The main difference that makes people recoil from the subscription model is this: when Autodesk stopped supporting Eagle standalone/permanent, people had multiple years to find an alternative and learn to use it, while continuing to use their old product. When Autodesk decides that Eagle in Fusion isn't working and decides to stop supporting it, you may have a month or less to figure out something else. That's the entire base of the complaining.
The difference for me is that when software becomes deprecated, I am still in control of when it will 'inevitably' stop working. I can decide to maintain the machine it currently runs on indefinitely, come up with a virtualized solution to continue operating it, and so on. It should be safe to assume that it will be at least possible to access the software, and therefore my data, for a decade or more, provided I archive the software itself and possibly the means of running it (unsupported OS image etc.). That is very different than the situation here, where a company can unilaterally prevent me from continuing to use the software no matter what I (legally) do for literally any reason they choose.
When access to my data, and for some, the product of their life's work, is subject to the whims of a megacorp, I get a little uncomfortable. There are several reasons for this.
When Autodesk in the future decides to stop supporting this product, do they decide to grant a perpetual no-server-check-required license to their users? If not, you will simply be locked out of your data with no recourse; this has happened with DRMed games many times when the company goes out of business or for whatever other reason turns off the license server. You have no control and no knowledge of when this might happen or how long they might deign to give you to get out.
If you switch to a different tool in the future or for any other reason (retirement? career change?) the subscription no longer makes financial sense to maintain. Do you keep paying Autodesk while you are not using their tool just so you can continue to access your data occasionally and non-professionally? Do you spend the effort to extract your data from their clutches and convert it to a more portable format? Do you accept that it's gone to you? None are appealing.
If (more likely when) Autodesk jacks up the subscription price to a point that it doesn't make financial sense, but your data is locked in to their platform, what do you do? You are completely held hostage.
It is not a comfortable position to be in. I'm really not sure why companies are willing to take such risks, but then I am just a hobbyist.