I got into a really good uni. I thought the degree was broad enough to cover all my interests and position me for a life in public policy.
I was a good student and general networker but I crashed and burned with my thesis. I got too excited about the topic and tried to cover too much. Finally, after much confusion, it became a last minute 3-day affair.
I couldn't defend it. I didn't have a thesis defence session though. It was more of a case where you have multiple meetings with supervisor and then you submit it. The feedback you get from the panel (who usually interrogates you in a thesis defence) is final.
In my experience, I would strongly suggest reading and practising the basics of compositional argument and writing before you attempt a thesis.But remember that a Graduate thesis is not considered or intended to be as thorough as actual research. Keep firm grounding to what you can achieve in 10,000 words or so. Don't try to move the moon. And above all, maintain clarity in your argument.
Those grading your graduate thesis will be less interested in your content and more interested in your ability to present it. So you don't need to be crafting e=mc2 or anything. You, ostensibly, need to demonstrate that you are capable of academic research and should be capable of learning and writing well enough to get into a PhD program.
Just my hundred rupees on the matter.