One thing I've been unable to ever see adopted is a true bottom up planning strategy, where the time to delivery is estimated from historical data. Say last X p

One thing I've been unable to ever see adopted is a true bottom up planning strategy, where the time to delivery is estimated from historical data. Say last X project took Y time, similar Z project will thus take Y time. And from there, the business plans timeline and delivery dates. The reason for this is that in practice I've found estimates are an indirect way to define scope. You need to ballpark the minimal viable product in a range from under a month, a month to 3 months, 3 to 6, 6 to 1 year, over a year. After that, its just about downscoping all the "good to haves" based on if there's time left from the desired deadline or not. As long as you delivered the "must have" in your timeframe it should be good.