For a native speaker? Not necessarily. There are many regional accents where the 'g' is silent or minimised: for example, the traditional Cockney speech of London, or the accents of some southern states of the US. For native speakers from these areas, this is a normal way to speak. Something which is normal is not 'bad practice'. For you as an English learner? Yes. Learners of English should learn and use standard pronunciation.

You will often hear native speakers omitting the "g" saying goin', playin' , walkin' But you should not do it unless you are bilingual. However "ing" is a single sound and the "g" should not be pronounced separately. It's hard to explain without sound. Here is a youtube about it. https://www.youtube.com/watch?v=BAc9qb76qEQ

There is no audible [g] in "-ing" for most English dialects. "ng" is almost always pronounced [ŋ] as in "bang" and "going." Consider these words: bag [bæg] ('g' pronounced as [g]). ban [bæn] ('n' pronounced as [n]). back [bæk] ('ck' pronounced as [k]). bank [bæŋk] ('n' pronounced as [ŋ] when followed by 'k' - 'bank' sounds like 'b-a-ng-k.') bang [bæŋ] ('ng' pronounced as [ŋ]). Now consider these verb forms: I'm going to work late today. (standard - going BrE [ɡəʊɪŋ], AmE [ɡoʊɪŋ]) I'm goin' to work late today. (regional variation - goin BrE [ɡəʊɪn], AmE [ɡoʊɪn]) I'm gonna work late today. (standard reduced speech - gonna BrE [ɡənə], AmE [ɡənə]) Here's a youtube video with a detailed, correct explanation of the differences between [n] and [ŋ]. https://www.youtube.com/watch?v=8bKIm60nK80