Integrated flash is still a thing in cheaper consumer cameras, that are mainly built to be used in full auto.
Integrated flash however has some drawbacks:
- Relatively weak, so anything that is not a close upper body shot is probably out of reach.
- As they are mounted very close to the lens, you not only get very flat lighting, you also risk effects like red eyes
- the proximity to the lens also can be a problem, when trying to mount a very fast portrait lens, which might be big enough to cast a shadow onto the subject.
- Small flash size will only give you super harsh light (softness of light is created by having a relatively large light source)
- Uses quite some energy from the shared main batteries
- Cannot be used as bounce flash, as they are faced straight forward. They would not be powerful enough anyway.
Cheap consumer cams however, are on the verge of becoming obsolete due to cell phone cameras. The added computational power in these can do what the flash in cheap cameras never achieved: create usable images in low light situations due to better sensors and automatic image post processing.
So, yes, small internal flashes are an emergency option only. And the images will be worse than that of a current cell phone in many situations. Most modern mirrorless cams can take images in situations where a small flash would not help much, apart from completely destroying any atmosphere the shot would have.
This means that while in consumer cameras you have a scenario of either add some light via tiny flash, which will most probably result in a about correctly exposed subject while the background drowns in darkness or having no usable image at all - the expectations and capabilities of a modern camera is, that the atmosphere of the scene can be preserved via using higher iso and reducing the resulting noise via processing. For example the Nikon D80 has an iso limit of 1600 (3200 with boost). A Sony a7 III has a limit of 51200 (204800 with boost). And I find that the noise is very well controlled until around 6400. After which it becomes more and more visible and has to be taken care of in post production. 204800 paired with a fast lens will produce an image even in situations where my eye is no longer able to see much. However, the image is nothing I would consider usable due to massive noise.
ISO examples of the a7 III (a current prosumer full frame mirrorless at 2020): https://havecamerawilltravel.com/photographer/sony-a7iii-high-iso-sample-images/
If you would like to enhance such a shot with flash, you would need to do things with the flash that is beyond what a built-in flash can do (using it off-camera, bouncing the flash against a wall or using a softbox, using color correction gels, manually controlling the exact amount of flash to balance it with the ambient light).