Not as simple as that. Not at all.
If a dps makes one mistake with their abilities it very rarely causes a death or a wipe. However if a tank or healer mess up even just once that can quickly lead to death or a wipe. That can be a lot of pressure. I've seen many wipes because a tank or healer was too slow to press a button or misjudged what was needed for the situation.
Healers and tanks very heavily rely on each other to play well. I've had some dungeon runs be wildly different despite being the same content simply due to the skill of the tank. I've had some tanks who made healing a breeze and others make it a nightmare. With dps...well regardless of how bad the rest of the party is you're still just doing your rotation. Your rotation doesn't increase in difficulty because the other dps sucks. At most you end up using some ogcds to survive, and maybe kite if things go really really badly. Tank and healer roles quite literally become more difficult to do if one of them is not very good.
That is partially why bad dps players are fairly common. In dungeons it is rarely super obvious if they're doing something wrong unless they're horrifically bad or you have a parser, which most people don't. It's especially even less obvious if the other dps is such a good player that one of them not being very good matters little. In dungeons there isn't a second tank or healer to carry a less skilled tank or healer. Because of this it tends to be very quickly obvious if the tank or healer are not good players. This can make the learning phase for those two roles quite stressful.
This is not to say dps is an easier role. It's just different. Dps get pressure in different places, namely savage because the demand for big numbers is often very high. Because of how important dps is in that content the pressure on them is absolutely constant as long as there is something to hit. Whereas for healers and tanks the pressure is on and off depending on what mechanics are happening.