Why do modern cars still have 2 and 1 on the stick?

Depends where you live. They use a CVT in their home country version of the Elantra hybrid. I suspect they will show up in the US. Seems like a simpler transmission to make but who knows.

Slow to a suitable speed before selecting a lower gear; you do not want to select second gear while trucking down the highway at 75 MPH. I suspect some of the smarter late-model transmissions with computer control will prevent the downshift from actually happening unless the car is going slow enough, but that’s not guaranteed for all cars.

“D” and “2” and “1” are all on the same side of neutral, so don’t mess with shifting to neutral first (there’s no point to this anyway).

When you select the lower gear, the car will lurch to a lower speed as the engine suddenly revs up. The faster the car is moving at the time of downshift, the stronger the lurch will be, and the higher the engine RPM will be after the downshift. If you’re in a rear-wheel-drive car and really hustling down the road when you downshift, the tires may briefly chirp.

You might consider experimenting with this just to see what happens. Find a long straight road, make sure there’s no traffic behind you, and slow the car down to 20, then select second gear. Now repeat it at 30. If that wasn’t excessively violent, try 40 - but you probably don’t want to be going faster than that for downshifting to second gear.

I would not advise shifting to first gear at anything more than 20 MPH.

completely false. the Aisin eCVT has one planetary (sun/planet/ring) gearset, and it uses the motor/generator to vary the speed of one element to let it act as a CVT. It has no fixed forward gear ratios (again, just like a CVT.) A typical automatic has multiple sets of planetary gears, and using bands and clutches selects which elements of which gearsets to connect together to provide the desired forward gear ratio.

what does this mean?

Conventional automatics are based around a planetary gearset. Hereis a good video of how they work. It’s not a function of meshing gears together as it is a function of locking a carrier. When the vehicle is at a standstill there is a torque converter which allows the engine to spin freely until rpms are increased. Imagine a fan that blows another fan. when the speed of the fan increases it produces enough force to drive the other fan.

One of the fun things about the old 2-speed automatics like the Powerglide in Roderick Femm’s family Nova is that when you stomped the gas down to pass on a 2-lane highway, it would downshift and you were then going 80 miles an hour in 1st gear.

Unless you are driving some VERY old cars you probably have never driven a car with drum brakes all the way around which was my point. Front drums went away in the 1970s.
Sorry for the confusion.