Thankfully it is a small 2 lb. or so gel-cell battery like is found in emergency lighting. the weight of the battery and the servo are pretty much offset by not having a cable, bracketry, and all associated linkages. Aside from a few idiosyncrasies, both of these MB SUVs we own is just as easy to maintain (but requires far less wrenching) as any "classic" I've ever had. Cost of parts aren't really any more than anything else of the same vintage. Sitting at over 300K miles on the diesel, and almost 120K on the gasoline burner. IMHO, compared to the '14 Audi Allroad and the '14 BMW 535GT that we had, it appears that MB makes the best all-around most well-designed, easiest to repair German vehicles. And they are made in the US. We bought them used for not really much more than other used SUVs of their vintage were going for since we're just poor country folk that refuse to purchase new anything ever again. No crazy expensive custom specialized tools needed to do routine things like brakes, oil changes, bulb replacements, alignments, axle shaft replacements, filter changes, etc. I can only think of one thing I can point to on the engines in them that I would consider a pish-poor design: plastic coolant fittings. And the stupidest thing I can see about it is having to fill the transmission through the drain plug. But I guess most of us boaters kinda already do this, so it's like second nature.
I don't know that they are any heavier than any similarly-sized SUV from their generations. They sure as heck don't feel heavy in the way they handle.
But to your point, I don't believe there will ever be a day going forward that we return to the simple pleasures of yesterday's automobiles. Too many multi-letter acronym governmental organizations have pretty much eliminated that option.