The age of electric flight is finally upon us

It's not negligible for its weight. You can always scale up an electric motor. The largest machines in the world (such as bucket wheel excavators) are driven by electric motors. Additionally, electric motors are much simpler to cluster into a distributed propulsion configuration than jet turbines are. That's why NASA's building the X-57 electric aircraft.

A motor that would overheat at takeoff power won't necessarily overheat at cruise and would be designed not to overheat in an aircraft application.

Motor control is not just on or off.

I'm not so sure! Have you ever heard the sound of twin-turbo regional airplanes in small airports? That sound is not from the turboprop engine, but from the propeller itself. Electric planes do have propellers and propellers are usually very loud. Actually much louder than turbofans!

Making propellers quieter has been an active field of research in fluid dynamics for decades but it's a very hard problem.

E.g. the Eviation Alice carries ~8000 pounds of battery and provides its nine passengers a range of 650 miles. That's undeniably a lot of battery and the energy density is indeed not great. However, it doesn't prevent it from flying. Transporting 9 people over that kind of distance for the price of charging that battery is a very disruptive cost improvement over the state of the art that involves burning hundreds of dollars worth of fuel.

It's the cost of fuel that's going to kill jet and piston engines. It doesn't matter how energy efficient they are when the cost difference with battery electric in the first generation is already two orders of magnitude. And while we have pretty much peaked in terms of fuel cost efficiency (order of magnitude improvements seem unlikely), that is definitely not the case for battery electrical. Cheaper and lighter batteries are basically happening. 2-3x seems to be likely within a decade or so. More may come after that. Electricity prices are also not a constant and seem to be dropping rapidly. So, if it's economical now, it's going to be far more economical in a few more decades. I think another two orders of magnitude cost improvements are likely.

For the same reason, hybrid planes are not likely to be more than a stop gap solution. They'd still be burning a lot of fuel which would raise the cost relative to small battery powered planes. I do believe that they will have an important role for longer distances; for the simple reason they'd definitely provide better energy efficiency. Ultimately, synthetic fuels generated using dirt cheap electricity may help bring prices down here but this will take a while and is not likely to be a very efficient way of using electricity (compared to storing it in a battery and using it directly).

As soon as battery powered planes are range competitive, which for short haul is happening right now, orders of magnitude cost improvement means game over for traditional planes.

Here's some back of the envelope math for you for the Eviation Alice vs the A319. You can buy a state of the art A319 for about 110M $. That same amount of money buys you about 30 Eviations (at the announced price of 3M $). You only need about 18 to match the number of passengers of an A319 (160 passengers). The A319 is very popular on short haul flights that are well within the range of an Eviation Alice. The difference is that one burns thousands of dollars worth of fuel and the other has an operational cost measured in the lower tens of dollars. There are of course many other advantages replacing big A319s with small battery powered planes. E.g. they make less noise and they can fly to much smaller airfields. The point here is that we don't need an electrical version of the A319. Big planes are only interesting because of the fuel economy. Small electrical planes don't have that problem.

The biggest bottleneck is actually not going to be batteries, engine efficiency, maintenance, or electricity cost but pilot wages and production volume of these new planes: we'll need a lot of them and with the cost of electricity already being low, pilot cost is going to be the dominant thing. As cost drops, ranges improve, and production volumes go up, the business case for operating an A319 will rapidly disappear. The Eviation arguably already challenges that. Autonomous flight, which is another thing Eviation is working on, will accelerate this. IMHO most A319s shipping today will be retired years or decades before their normal projected end of life because of their operational cost vs the cost of products like this.

This is why Eviation has a full order portfolio. They'll be selling these things as fast as they can build them. Others will follow. This is only the first generation of their product. I expect great things from them and their competitors in the years to come.