It is extremely difficult to market an indie game without already having a following and a good game. It mostly comes down to luck, first impressions and resilience. It's difficult to get noticed on places like YouTube but the advantage is you can post as many videos as you want without being considered spam. You can post in game development communities, including specific ones (e.g. game engine, genre, itch.io) but you're very unlikely to get more than a couple people interested. If your game is Let's Play-friendly, you can try politely sending download keys to smaller YouTubers since they will do the marketing for you and give valuable feedback.
Thanks for the honest and detailed response! I completely understand that marketing an indie game without an existing following can be really tough. I'll keep in mind the importance of first impressions, persistence, and maybe even reaching out to small YouTubers for exposure and feedback. Your advice is incredibly valuable!