It's a dark L, and in the same way "dark matter" is so called because we can't see it, the "dark L" is so called because we can't hear it. It modifies the shape of the tongue which affects the sound of the vowel/consonant pair, but there is no actual L sound.
The sounds /l/ and /r/ are problematic because in many cases there is no "fixed point of articulation" - i.e. what parts of your mouth and tongue touch together when you make those sounds.
Most American English speakers make an "l" by touching their tongue to their alveolar ridge (the gun right behind and above the front teeth), but there are many other ways to make a sound that is perceived to be an "l", the "dark l" being one of them. Because there is often no point of articulation, the "dark l" sounds like a vowel (or a semi-vowel / glide) to some people. [Vowels don't have a point of articulation - i.e. the parts of your mouth (teeth, tongue, lips, etc.) don't touch each other during a vowel]
No native English speaker I know pronounces "walk" with a alveolar l - which would sound like "wal-uk" Rather, they pronounce it as a dark l - more like "wahk" In fact, there are many native English speakers who pronounce "walk" and "wok" (the Chinese cooking pan) identically.
It's not artificial! It's how everyone pronounces it. There are loads of similar words where we pronounce the 'l': boulder, folder, colder, holder, older, shoulder, smoulder.
Yes. but while people do use an alveolar l in words like "boulder" and "shoulder" in careful or semi-careful speech, a lot of people also essentially "drop the l" in these words too. When I (jokingly) affect a non-American accent , I pronounce these like "bowda" and "showda"