These days they might be more open to such as concept because several subsequent shows have demonstrated season long arcs like that can work.
Season 4 was produced 1997/1998 and most TV was still of a generally stand-alone weekly nature. There had been 'Murder One' within the legal drama genre but it got cancelled after two seasons and had to be rejigged a bit even for it's second year.
Now, what with 24, Battlestar Galactica, later DS9 and the mini-arcs of ENT it's been proven that such stories are viable.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist