Toyota had issues with some
Toyota had issues with some engines' oil gelling (thickening). This caused engine damage for which Toyota got blamed. As a result of this, on my '09 Corolla, the "maintenance light" on the dash flashes for a few seconds at start-up then turns off. This begins at 4500 miles. At 5000 miles the "maintenance light" stays on constantly. There was also an information card in the glove box addressing oil gelling and strict adherence to the 5000 oil change. I grew up in an era where 10w-40 was the oil of choice for vehicles. As far as taking a deep breath, I did that when I put 0w-20 in my Corolla. The 2019 Camry uses 0w-16 weight motor oil. I suspect the new RAV4 will use that weight oil since its powertrain is similar to the Camry's. The latest motor oil rating is SN Plus. This is to address issues that can cause engine damage, especially those small engines running turbos.
On my Silverado I use the OLM as a guide as to when to change my motor oil. I change it around 10% which translates 6000 to 6500 miles. Since the vehicle is still under warranty, I change the oil per manufacturers specs. I use 0-w-20 weight oil as that is what Chevy recommends.
As you said, motor oils have been improved over the years. Totally agree. As far as the lighter weight oils go, that is to help manufacturers meet CAFE standards. I do notice on Mobil 1 containers that whenever they make a claim about their motor oil, they use the 5w-30 motor oil as their reference oil. I wish they would use a 20 weight oil to base their claims on since it reflects where the industry is today.