They watched the news. I just came back from holidays in Italy from my family, and they would watch the news from 3 different channel the entire meal.
The meal lasted 2 hours each time. (That's 4 hours per day, equivalent to doomscrolling)
And yeah the excuse to "stay with the family" is still there, except me and my wife refused to force our kids on the table: the kids will stay at the table if you talk with them, otherwise it's your (grandparents) fault
Between the morning/evening news, a sports game or TV movie, reading the newspaper, and a bit of novel reading, my parents in the 90s were just as physically-available-but-in-their-own-world as somebody scrolling TikTok for 4-5 hours a day. I think the difference is that reading the newspaper isn't literally a dopamine-fueled addiction and turning the page in a novel isn't the psychological equivalent of pulling a slot machine lever.
We have lots of evidence about how harmful it is to have parents that are in the throes of gambling addiction. Folks, it's not good for the children. It's in fact pretty bad, even if they don't gamble away the home equity and the college fund.