Speaking as a linguist, speech just is - it's neither good nor bad - but that doesn't mean that I find all its varieties pleasant to listen to! Intrusive r is here to stay and it is by no means only 'sloppy speakers' who use it.

When we speak, particularly when we speak quickly, parts of words get elided - merged or omitted completely - that's just what happens naturally. Don mentions that a glottal stop 'should' come at the end of words, but think of 'lie in', 'tied up' - in UK English they would almost certainly be run together.

There are as many variations in language as people on the earth.