I suspect the main concern is that customers who purchased the Gold Lifetime package believed they were entitled to all future updates and additional functionality for the lifetime of the product.
If that is the case, how were those expectations managed at the point of sale? Was it made clear that "Lifetime" referred only to the functionality available at the time of purchase, and that future premium features could be excluded? If so, then any misunderstanding may simply stem from customers interpreting the offer differently.
My view is that the business has recognised that the Lifetime model will eventually reach a saturation point, where revenue from new Lifetime purchases begins to decline. At that stage, relying solely on Lifetime sales is unlikely to generate sufficient income to support ongoing development, maintenance, and future innovation.
I completely understand why the business has chosen to introduce a new commercial model. However, I can also appreciate why customers who previously purchased Lifetime access may feel differently, particularly if they believed their purchase included access to all future functionalities. Ultimately, much depends on how those expectations were originally set and communicated.