With
A1: a start date....2019-07-15
and this list of dates to skip:
D1: 2019-06-01
D2: 2019-08-15
This regular formula returns the date that is 90 days from the start date, not counting the dates to skip:
B1: =WORKDAY.INTL(A1,90,"0000000",D1:D2)
Note: this pattern "0000000" flags weekend days, beginning with Mondays, with 1's. 0's flag work days.

In that example, the formula returns: 2019-10-14 (skipping 2019-08-15)

Is that something you can work with?