There are many ways to reduce and prevent spam.
You can ban individual IP addresses or entire ranges of them (this blocks all subsequent posts from the same source, regardless of how many throwaway accounts they may create). You can block all posts from specific countries and regions that are known spam-havens (this is more problematic as the innocent are swept up along with the miscreants, including those forum veterans who might be vacationing in one of those places). You can search the content of each post (or just posts from "new" users) for specific keywords or phrases (or characters - eg emoji) and block (or temporarily hold) any that match a specific score criteria. You can even write complex AI that learns from spammers' behavior and adapts. You can make all new accounts ("new" however you define it - typically number of posts, but can include other ways of vetting for trustworthiness) subject to these rules, or all accounts. You can use familiar, simple technologies (captcha, how many bicycles in the picture, ask a simple logic/arithmetic question, match an image with a word form a list, etc.). You can do all these things together, or mix them. You can do them only for un-vetted accounts, later removing the restrictions. You can use any of these measures on all posts, or only on some that meet specified criteria. You can just have one person who manually watches the forum 27/7/365 (but they've gotta sleep sometime), or you can spread that task among many. You could do some of these things only on long holiday weekends and/or when staffing is thin.
There are plenty of options. All of them cost something (development, implementation and maintenance costs, training, and any would also have non-monetary costs ie annoyance, adding friction for all users, changing established practices). Not implementing them also has some costs (noise, general annoyance, the forum becomes less attractive to users and thus less valuable to the company).
Business management has to decide if/when the cost of making changes is justified, and would outweigh the costs of living with the status quo. I'm sure they have considered their options before and have decided they can live with things they way they are. Two years into a pandemic that has shrunk their business income to near zero is probably not the best time to try and sell a forum upgrade, so I would set all our expectations realistically. At some point, conditions may change enough to prompt a re-evaluation. If the spam becomes bad enough, or they start seeing some positive cash flow, that might tip the balance, but this is a business decision, and times are tough for travel businesses. But while the forum is certainly valuable, it is very likely viewed as a cost to the business, not a source of income. Given that, and the state of things, I suspect an anti-spam investment in the forum would be a hard sell. I'm willing to do my part (or not, as preferred by those that run things). But I would not expect to see any significant changes for the foreseeable future.
Just my 4 cents.
