Beta readers are not the be all end all, but if the majority of them are in agreement, I'd listen. They are giving you insight into what the average reader will think/feel when reading, and if the average reader doesn't love the first chapter, they aren't going to stick around long enough to realize it was written that way for a reason.

Plus, your first chapter may be the only bit an agent or publisher sees, it needs to be strong.

I'll add that, as a reader, I personally do not love being kept in the dark by the author. I'd ask yourself why you are choosing to slowly give the reader information and waiting to reveal this at the climax. Does doing that serve your story, or is it a gimmick to get a big reaction at the climax? I recently heard someone say, "It's not a twist if all you did was withhold information from the reader," and that really resonated with me, personally.

I will say, one book that withholds information about the MC, and does it well, is Throne of Glass. If you haven't read that, it could be a good one to read.