You can justify maybe up to one year of lag with "we overscheduled, oops". But twelve months should be plenty of time to clean house and get things sorted out. (WIT Studios were actually the ones doing Attack on Titan when they had the four-year break between seasons 1 and 2, and I don't approve of them doing it either—however, the reasoning behind it seems to have been marketing-related rather than poor scheduling.)

T'be honest, it looks to me like the management team at MAPPA has bitten off way more than they can chew, and that they've been following that pattern for a while. It isn't a matter of taking their time or not, it's a matter of not accepting more work than they can actually do.