Well, I think the rest of the context before that is important too. First he blames Hermes for making him forget; that's the root of it all. Then he laments the 12k years of suffering he had to endure, and says he'll give Venat no thanks for her role in orchestrating that... although he acknowledges that their methods wouldn't have gotten humanity to this point. These "methods" are basically what he's been doing these last 12k years -- trying to sacrifice more life to Zodiark to bring back their past. They tried already to stop Meteion in the past and failed in their "fair chance" (according to Hermes's rules, anyway). Venat and the WoL were always the sort of Plan B that Emet-Selch himself helped to orchestrate in Elpis (although he forgot that he did). He obviously has a huge benefit of hindsight now to see that the ancients were misguided from the start, and so they never got the point of what Venat was doing and why.
The "spilling the beans" option was always there, but a big risk. Venat had one good lead of a possible alternate solution if the Ancients failed, which was the WoL. She herself explained the risk of getting Emet-Selch, who was on the convocation, involved, which could result in Hermes being thrown off the Convocation (at best, or retaliation at worse) which would deprive humanity of probably the most useful player they could have on their side given his research, and could also jeopardize the one other lead they had. So it's basically a two-pronged plan: hope the Convocation is successful and make sure all the best minds are working on that, but protect the backup plan so that you can execute it if need be.
So yeah, if someone were to make a sweeping statement like "there's no possible conceivable way the Ancients could have ever figured out a solution on their own," that's obviously wrong. Hermes himself created Meteion after all, so even without being able to directly manipulate dynamis, they could create more life that did (in a way other than sundering). If it weren't for Hermes's gambit, the memory wipe, and the knowledge of the future Venat had through us, they might have come up with other options. But yeah, the issue for Venat is that straying from the path could mean closing that door, and she at least knew for sure that there was a chance with the WoL.
I guess, in other words, the Convocation's job was Plan A, and Venat's job was Plan B. You're criticizing her for not exploring Plans C (through Z), but if she did that she might have forfeited Plan B. Whatever she did was taking an unbelievable risk, so she chose the largely-known path rather than the unknown one. And yeah, she deserves both criticism and acknowledgement for it, which is what Emet-Selch offered.