Definitely true. Some of the best "slapchop" paintjobs are actually just people who were really good at painting in the first place simply showing a handful of steps and providing the "and I drew the rest of the owl" result.Plenty, most of which P1138 covered in his reply, but he forgot one of the most important; you'll never get better at painting.
Because slap chop is so mindless and not similar to any other style of painting really, you won't be able to pick up any other skills besides maybe dry brushing. Compare to doing something harder like layering or glazing. Yeah those first models are going to look like shit, but there's so much room for growth through practice than something like slap chop.
If your end goal is just getting models on the board I guess it's a solution, but if you ever want to get good at painting, I'd just dive in to more traditional methods.
I would say though, if you can avoid the pitfalls of it(which kinda requires already having a decent amount of painting experience), doing slapchop or some other potentially time saving method for 100 basic infantry and then saving the "real" paintjobs for your characters and centerpieces or whatever can also work. Which gets to another issue with a lot of youtube painters; yeah they'll say they put in 10 hours into one character and it looks great. Most of them aren't painting full armies like that though(most don't actually paint armies at all really, you'll find a lot of the people on mini painting channels rarely if ever actually play anything) since most don't have the time for that(and painting an entire army in the same color scheme for a years worth of youtube videos once a week doesn't make for content people will continue watching).
Another point about painting in general is the more you paint, the faster you'll get at painting at your current skill level, Then continue saving the 10+ hour jobs for a single character/centerpiece/whatever for when you want to try improving, using new techniques, etc.
Admech just got a new KT a little while back. Could just swap the deathwatch out for them and play an analog version of that mechanicus video game(that's what popped into my head when I saw this box, and it seems weirdly obvious for GW to have not paired the teams up that way).I think it’s neat they’re doing Into the Dark over again but keeping it Tomb World focused. Hopefully some decent Ad Mech models coming down the line to go with it too. Would be neat to get 2 sets of the terrain, set it up ITD style for the 3 player option and use Necrons as NPCs with a neat rule set of how they activate and when. Glad they’re fucking finally adding Death Watch back into Kill Team since they function as a kill team.