Let's say you, dear reader, were attending a local art exhibition. In this scenario let's say you are not an artist yourself, as is the case with most. Attending the gallery, you find none of the pieces hit you in any special way. The art just doesn't seem to be working for you for some reason. Now let's say you leave that exhibition and discuss it later at a coffee shop with a friend. When discussing it, you might express how the art wasn't all that great, or how it didn't make you feel anything. But what I'm guessing- even though I don't know you- is that you probably aren't going to attack the skill of the artist or claim that they aren't good at it. Common sense, right? Even though it doesn't work for you, that doesn't mean it's objectively bad (although some critics of modern art might contest). If this seems like an odd thing to bring up, let me draw your attention to the fact that this is indeed how many express their feelings about acting and performance art every day.
Presuming first and foremost that acting is indeed an art form- which it is- it should therefore be critiqued as art; it shouldn't be discussed as a matter of whether or not the creator sucks at their job. The true problem lies in discussing acting in layman's terms. As stated above, a non-artist isn't likely to see a renaissance painting they don't care for and then claim that the artist did a bad job, or that they could do a better one. I despise gate keeping as much as the next person, but I feel as someone training in the field of acting it irks me when someone who doesn't do theatre or film (be it critic or performer) claims that someone is a bad actor.
Sure, there are definitely some bad actors out there, but this is an issue of vocabulary. Again, trying to stave off the gatekeeping here- we need to think deeper about why a given performance isn't working. Rather than it just being "bad acting" or a "bad performance," engaged it critically. Why was it "bad"? What didn't work for you? What aspects were not believable, and why weren't they believable? It's also worth considering that their supposedly poor performance could be the result of bad direction. Acting deserves the same level of scrutiny as painting, or photography, or music. There are techniques here; it's not so simple as talent.
That's perhaps my biggest problem with the current way we discuss acting. Everyone seems to think that acting is just talent. You either have it, or you don't. Newsflash: like every skill, acting is trainable, attainable, and for everyone. So the next time you walk out of a show and think, "man, that actor/actress sucks," maybe it's time to re-frame your point of reference and think a little bit deeper.