Sign of the times too, sadly. A larger forum I moderate went through a not great forum upgrade and it just accelerated the already obvious decline in traffic and participation. Like this one it predated much of social media and some areas were languishing as the conversations naturally moved to more modern / real-time discussion on social media and more recently Discord over the last several years. Gradual at first, and then it accelerated. They went through almost the same posting decline patterns we've had in our sports section, from numerous threads each NFL Sunday just trickles of activity on occasion in a single thread that covers the entire season.
Can't say there's really a 'fix' when the obvious seems so inevitable. You could start a Discord server but that's not revenue generating unless there's some form of new membership you could generate from it - and if so, what would that be? The core audience of the site is still the satellite business/customers, a business that has rapidly atrophied over the last few years as we're all well aware. I suspect many of those who have posted for so long wouldn't be interested in newer solutions like that, either, creating a new hole to dig out of. At the same time, there is the balance of not pushing people away with the type and volume of ads to keep the site viable, people who have so many more options now than to create an account and keep coming back to a traditional forum when they've grown up with all these other more readily available options.