You are not describing enshittification. I do recommend looking up Cory Doctorow’s writing on the subject to get a better understanding. (And yes, my comments may have drifted from it somewhat, too.)
What you are describing may indeed be more like typical run-of-the-mill capitalism, but again, there are variants.
Dr. Martens boots’ quality may have deteriorated as a result of owner decisions to expand sales volume at lower quality and outsourcing/exporting the manufacture to other places, all to maximise short term profit.
An equally capitalist owner might have decided to maintain or ramp up quality, limit sales volume (=exclusivity) and raise prices.
Who would have made the greatest return on capital over the longest time period? Who knows. Cost of capital, price elasticity, cost accounting, etc, are tools for the market capitalist to play with.
Yes, it does seem like nearly all capitalists these days are more of the former school, but some are not - a well-regulated market economy has room for all such strategies to compete.
But none of the above is really at the heart of enshittification - although Cory’s description of it as it applies to online platforms, does extend analogously to other capitalist activities.
And what @gatto said. Have a sip of Coke on me. 
