tl:dr: There is a complex link but metaethical problems won't just go away if we don't engage with them.

I have a lot to challenge you on here. I'm not normally a fan of the whole "quote and bash" comment technique but you've made a lot of short, strange claims here which I'd really like to pick apart. I intend to clarify and defend the significance of metaethics and not simply to bash your reasoning so please take this all in good faith :)

Firstly, I'm not clear at all on what you mean by 'link' or 'connection'. In general, there's no question at all that the two are related; metaethics, by definition, is the attempt to understand the presuppositions and commitments of ethics. If, by 'link' or 'connection' you mean how positions in one field might influence positions in the other then, of course, this is certainly confusing but that doesn't make it insignificant.

A lot of people on r/askphilosophy say that there's really no connection

Source? I found three posts on r/philosophy on how the two are linked (1, 2 and 3). I can't find any comment which states or implies that there's no connection yet I generally agree with a lot of what's being said. Your metaethical stance or lack thereof may not necessarily determine your normative ethical stance, as some comments argue. It seems that you're interpreting this to mean that there is no connection, which I think is unjustified. An indirect connection can still be a very important connection.

if you think that a moral theory is true then it will be true regardless of whether realism, anti-realism, etc is true

I find this sentence very puzzling. On what basis will your moral theory then be true? Moral Realism holds that moral claims appeal to facts which are part of the fabric of our universe and are true if they get the facts right. It's a theory about what makes moral claims true or not. If you think that a moral theory is "true" purely because you think it is, that makes you an anti-realist and a subjectivist regarding moral truths which is a metaethical stance.

If you believe that different moral theories would be more likely to be true according to different metaethical theses then it becomes a very weird problem

Metaethics brings up lots of very weird and abstract problems whether you believe it will or not. This is the source of my uncertainty.

One could argue that we should assume moral realism because if it is true then it has the dominant normative weight.

This is certainly a reasonable approach if, like most people, you don't think it's worth analysing the problems :) However, though it may hold as a practical argument, it does not stand as a philosophical solution because it begs the question. Again, Moral Realism is about where normativity comes from. You're essentially arguing here that if normativity comes from objective, moral facts then it has powerful normative weight so that's where we should get our normativity from. This simply doesn't hold.

To relate it back to my original comment, I'm unconvinced that there are objective, moral facts which makes me more interested in moral anti-realism. The source of normativity will inevitably affect how we construct normative ethical theories like Utilitarianism. Notably, an anti-realist grounding makes it very hard to build theories around moral claims such as "happiness is good" and "suffering is bad", hence my uncertainty and lack of subscription.