By the time you get to variable valve lift and timing, the complexity of hybrids is either a wash or in favor of the hybrid when compared to a traditional engine. Electronics have been integrated in vehicles for generations now, and going hybrid lets you get rid of components and reduce overall mechanical complexity. It's not "two separate systems", it's just the obvious endpoint for internal combustion engines (and a process that is both a century old at this point, and already mature in other industries), because you get a strictly better machine from both a performance standpoint, and a design and engineering standpoint.
Not to mention, much of the complexity in ICEs comes back to cooling and lubrication, both of which are also concerns in BEVs.
You are not comparing complexity to an ICE though. You are comparing to a BEV.
A plug-in hybrid is a much more complex machine than a BEV.
This is what the person that I was responding to wrote, and it's objectively wrong:
>Hybrids are the worst of both worlds when it comes to maintenance. They have their benefits and are key to fighting climate change, but mechanically you inherit all the problems from both sides.
Also, much more complex is a value judgement. Complex in what way? High voltage electronics isn't exactly "not complex", and the coolant loops in BEVs are more complex than those in regular cars, because the tolerances are tighter.
I'm going to go out on a limb and assume that you mean mechanical complexity, but even then, that's not a given for ICEs. Gas turbines can have as little as one moving part, and there are piston engines that can get away with as few as four (the piston-conrod-crankshaft assembly and a compressor wheel).
At the end of the day, a good design has the minimum amount of complexity necessary to perform a given task, and no more. Given that BEVs are fundamentally unable to replace ICEVs in several niches (e.g. those relying on on-street parking, off-roading), maybe a little more complexity is warranted? As is, they aren't a 1:1 replacement for a standard car, and that's okay, but they're being marketed as such which is a recipe for failure.