I agree that a BEV with no engine should be less complex, but I don't think ICE+battery hybrids are necessarily more complex than ICE alone. Most hybrids eliminate the complicated parts of the transmission -- multiple sets of gears that have to be moved in and out of place. The Toyota hybrid system, for example, has a single set of planetary gears, and Honda has a single speed transmission with just a clutch to engage. They also eliminate starter motors (replaced with a much more robust generator motor), alternators (replaced with a solid state DC-DC converter), and other components hanging off of engine drive belts (electric AC, etc).
Yes, internal combustion engines themselves are complex with all the pistons and valves and injectors and all, but decades of perfecting them have made them extremely reliable with very little routine maintenance. At least from some manufacturers (Honda among them).
For me, and me alone, the PHEV fits my needs extremely well -- I didn't have to buy and don't drag around tens of kilowatts of battery that I don't need most of the time, yet 95% (99+% now during COVID) of my driving is electric. And when we decide to take a road trip, we just fill up and drive like normal.
Nothing wrong with anyone making a different choice, whether that they are fine with a pure BEV (because they don't mind planning longer trips accordingly, or have a 2nd car anyway) or that even a PHEV isn't worthwhile, but for me it's the sweet spot in technology right now.