Do you need go-to-market strategy at early stage?

My startup is pre-revenue. Last week i was in one of the local AI Startup meet up, and attended some GTM office hours hosted by some folks from big company marketing team.

Was told Go to market strategy is necessary, need professional helps, it will guide how i run growth campaigns(cold emailing), branding(color). and that i am not able to aquire customer maybe because i don't have a go-to-market strategy, and later on followed by a invitation for deeper GTM consultation(paid).

Because i haven't successfully gotten any customer, i cannot rule-out this possibility. But i've watched almost all YC videos on how to get first customer,

1. having a GTM is never mentioned not to mention as a mandate

2. in fact, from one of the Aaron Epstein's video, a sincere, manual, email works best, with a razor sharp ICP, this doesn't sound GTM at all, it's just doing this one, hard-coded step, no strategy is needed.

I would love to hear from you folks on your take before i either go work with these GTM folks, or follow the linear, hardcore step that YC/others have recommended.

Time is money thus asking for advices.