It was entertaining because it was meant to be a show.
Embarrassing for combat sports
Embarrassing for boxing standards, I think you mean.

Honestly, I say this as a pure MMA/UFC fight fan...the refined striking of boxing is not something I'm used to. Nor is the nuance of the "cheat" moves that a seasoned professional like Mayweather will use to get out of a dangerous situation in boxing.
So to me, the Mayweather/McGregor fight was exciting to watch. I think Joe Rogan and Brendan Shaub felt the same way about it, and I think Mayweather stated that he felt that he won 4 or 5 of the ~10 rounds, if there was an evaluation of each round. From my memory, that was about right.
Anyone watching the fan with boxing knowledge probably had a lot less faith in the fight ultimately going to McGregor, but as a non-pure boxing fan, I thought it was great to watch. Although it was annoying to pay $98 CAD [$0 USD] twice to buy it, only to ultimately end up streaming it because of server problems.

Georges St-Pierre said that even using MMA gloves would have completely changed the outcome of such a fight. Because of the ability to dirty box - I guess small gloves change what you can do in the clinch. So that is why to me, as a fan of MMA and not boxing, it was cool to watch.
Funnily enough, after watching Holyfield vs. Tyson II, I thought to myself "UFC striking is NOTHING close to professional boxing."