Bots are better in Vermintide 1 because the bot mods are better. See DifferentBots mod for V1. Note its features and update release dates. It has more features and has more active development than V2 bot mods (sanctioned or otherwise). It also has a ‘bot performance reduction’ functionality, so if you think the bots are too strong you can actually gimp them in various ways.
The most often mentioned bot complaint in V2 (and V1) that I’ve noticed is: bots chasing after specials with melee weapons, causing them to facetank long-ranged specials’ attacks, trigger patrols, and ignore revives even if the player is right next to them. The V1 bot mod can be set to not allow bots to chase after long-ranged specials, working around those issues.
Another bot complaint I hear about in V2 (also a V1 bug) is bots getting stuck (if not also facetanking) when a rating gunner is firing, as lamented here. The V1 bot mod can be set to ignore ratling fire, so they wouldn’t be stuck.
That’s an old post from 2017 (before Vermintide 2 was even announced) and is specifically about Vermintide 1. It is hardly relevant to V2. It is countered by the fact that Fatshark themselves introduced a bot improvements patch for V2 and that the V2 Bot Improvements mod by Grimalackt (who is also the author of the V1 bot mod discussed in the comment you linked) was actually sanctioned by Fatshark.