Like with changing the Greedo scene, it cheapens the villains and mades them feel less threatening. This reduces dramatic tension and makes us worry less about whether our heroes will make it out alright. If a hired bounty hunter misses from 5 feet away, why should we worry about government soldiers hitting anybody from a further distance?
If Han can just brazenly talk back to his gang leader like that, why should we be worried about when they all get captured in Jabba's Palace in Return of the Jedi? Surely if Jabba is okay with letting Han off with a warning this time because he's been promised the money in advance, then there's no reason to believe Jabba won't gladly accept the payment in Jedi since Han can more than afford it on the spot.
What's that, Jabba doesn't care and would rather have Han killed and forgo an amount of money greater than what was owed him? But then why was he cool with it in A New Hope?
I mean imagine if a gang leader was like:
Gang Leader "Yo, I want your 2,000 you owe me."
Gang Member "fine just give me more time and I'll pay you a little extra"
Leader "alright since I'm a nice guy, I'll let you go with that. Just pay me 2,500 next month"
6 months to a year later
Leader "that's it, you didn't pay me on time, time to die"
Member "But I have the money with me. Just uncuff me and I'll get it out of my briefcase for you. Here, since I took much longer than promised, I'll just let you have 5,000."
Leader "Who do you take me for, a pansy forgiving doormat? I have plenty of money already and I don't care how much you can pay me now. I'm going to execute you anyways just to set an example for everyone else to see, that there will be unforgivable consequences for failing me."
Does that sound like the gang leader has the same character and personality? Does he/she behave the same way in one instance as another? This is contradictory behavior without any explanation as to why
Incidentally, if you watch all three back to back to back (like I did this May 25th), you might notice something similar with Darth Vader. He's just one of what is presumed to be many fear imposing people working for the Empire. Then he's an unforgiving badass in ESB. Then right at the beginning of Jedi, he's like "the Emperor is not as forgiving as I am" and kind of is a weak character who feels trapped in the situation, rather than someone who gets off on being a BAMF.
There's nothing wrong with a character having an arc but even in the original versions of the films, Vader's transformation feels rushed, abrupt and yes even forced. (get it?)