Agreed Mr Maim.
What the Vickers most certainly isn't, is a knockoff. Most folk who understand the term, know a "knockoff" to be a cheap copy...which the Vickers definitely isn't. The Vickers was an evolution and improvement over the Maxim design. Good enough to remain in service for over 50 years with the British military.
In comparison to other water cooled (WC) belt-feds, it's at the top in my opinion. It was fielded in .303, 8mm and .308 (others?)...it also readily converts to 54r. I don't believe any other WC belt-fed offers the same caliber versatility. Though parts are nowhere near as cheap and plentiful as they once were, availability / cost is still better for the Vickers than the others. The Vickers is simply lighter, adapts to more calibers, tripods, and is just more elegant in my opinion.
I would argue "who needs an MG08 when you can have a Vickers!"
In comparison to other belt-feds, the lagging WC belt-fed market is more than just cost of ammo. With the exception of the few 5.56 belt-feds, all of them consume expensive ammo. Parts availability and cost for air-cooled LMGs has taken off as well. I think it's the additional complexity of the water cooled feature, less hardware to tote around, perceived simplicity and the fact that air-cooled quick-change barrel LMG platforms are more modern and perceived by a younger buying market that way. 100 yr old WC guns are simply "complex ancient relics" to much of the buying market, which continues to get younger.
I sold off my MG08, 1910 and MG34. Not because any of them were bad...though the MG34 was finicky and the Maxims were another level of big / heavy that I was ready to move on from.