Anyone can take responsibility for defending some ideas.
People can defend different but overlapping sets of ideas and still help each other.
To the extent other people do useful stuff, it’s less work for you. To the extent no one else helps defend the ideas you care about, then there’s a lot of work for you. Though if you have little help, usually you’ll also have little interest from critics, thus reducing workload.
Dead people can be useful. People you have never spoken with can be useful. If they publicly write anything good, you can use it. Similarly if someone disagrees with you on many points, they still might write something useful to you about a point of agreement.
Over 50% of the work in rational debating is reviewing literature, organizing the arguments in the field, and responding to criticism with cites/links and maybe short explanations, but not substantial new arguments or writing. Most serious debates should be primarily about ideas that existed before the debate began – trying to sort out what arguments exist, which are already refuted, which have no known refutations, etc. – not about new ideas people come up with during the debate.
If you have anyone willing to help you, you can delegate some work.
Even without any delegating, other people will sometimes answer questions, share links, respond to arguments, etc. So that helps you. Your job (if you take responsibility for truth seeking regarding some ideas) is to monitor the situation and participate when and where needed, not to answer everything personally. If other people answer stuff in ways that satisfy you, that’s fine. If no one does, then you should take action. That’s what being responsible means. You ensure the answers given meet your standards, whether that requires you personally answer something or not.
A debate policy and debate methodology can help so you aren’t just engaging in freeform debates with anyone who might quit at any moment. Lots of people aren’t very serious and don’t want to put much thought and effort into their claims. You need ways to deal with those people efficiently so they aren’t a significant burden. That means referring them to existing writing or asking them to commit to a specific debate methodology (most of the unserious ones will voluntarily opt out – basically admitting they don’t have a serious criticism that you need to answer). You don’t want to spend significant time on hit-and-run critics who don’t try to take responsibility for the quality or correctness of their own arguments.
If someone has one reasonable question/concern/criticism and doesn’t want to debate further, that’s fine and it should be addressed. But some people will try to make a bunch of poorly written arguments that don’t contain new ideas. They may also write of insults. You need some constraints on how you engage with those things. You don’t want to just silently ignore it while having no failsafes in case you’re misjudging something, but you don’t want to get drawn in to bad discussions either. So the solution is to say some conditions for continuing, including methods to be followed, and they can either meet or discuss/critique the conditions. But anything else they do can be ignored.
You can write this stuff generically as a standard policy, and if it’s linked prominently enough and shared often enough then you don’t necessarily even have to repeat it every time with each new guy. If it’s really easy to find the policy and they don’t find it, that’s an indicator that they don’t care (or are incompetent). It’s like how sometimes you say “That is answered in the FAQ” and give a link, but you don’t have to do that every single time because they could find and look at the FAQ themselves if they cared to.
Anyone/everyone who cares about ideas can do this. There’s no need for central leadership or coordination between people with similar ideas. Leadership and coordination are fine and can help, but they aren’t mandatory. You just need some kind of public forum where you can speak and critics can speak. You don’t have to own the forum or be a moderator as long as your discussions are on-topic for that forum, allowed, and nothing important is interfered with by moderators. Broad discussion forums instead of single-topic forums work better so that e.g. discussing your philosophical premises will be allowed. Even if your ideas are all about (without loss of generality) chess, a critic could challenge some of your philosophical premises, underlying assumptions or discussion methodology, and that could lead to discussions that are worthwhile but are off-topic on a chess forum.
Anyone can specify what ideas they believe, say they are open to criticism at a particular forum, monitor for criticism relevant to them, and address criticism that no one else addresses. Anyone can do this primarily with links, cites and short explanations, and only occasionally create substantial new writing. If appropriate pre-existing writing doesn’t exist, you have a problem. Why did no one on your side ever write down adequate arguments to address that issue?
Is your side new, tiny and unpopular? If so, fine, you’ll have to do more work to write things. Keep in mind that recently-developed ideas should be viewed with greater skepticism because they haven’t been exposed to much criticism yet. (You should view your own ideas that way. You can be more confident if you haven’t changed your mind for a few years than if you thought of an idea yesterday. That does require the idea actually coming up and get thought about again sometimes during the few years, rather than getting no additional consideration over time.)
Any time you write something new, it hasn’t stood the test of time, and most potential critics haven’t seen it, and also if you aren’t popular then probably no one will care and look at it. If you can usually agree with existing writing from people who have gotten substantial attention, that’s better. If you can’t – if you think every popular author is wrong – so be it, but then you have a harder situation to deal with and should be willing to do more work.
(I myself do quite a bit of debating work, and write lots of new stuff, despite having significant literature to draw on from prior thinkers like Karl Popper. That’s partly because I want to and choose to. I’m trying to improve on Popper and develop new ideas even though his arguments were adequate to win many debates.)
If debates mostly involve cites, links and short explanations to help organize, connect or customize existing writing, then that is less work (given that you actually know the literature you’re claiming is correct). A lot of people avoid this because they don’t know the literature on their own side well and they think reading it would be too much work. Instead of reading, they prefer to write new, half-baked arguments that are kinda similar to existing arguments but with semi-random changes that aren’t designed to improve on the existing literature they haven’t read. It makes more sense to read the literature first, see if it satisfies you, and if it doesn’t then develop some new ideas with changes designed to address specific flaws you noticed in the existing literature.