Falcon Heavy's lateness never mattered
Payloads that were to originally fly on Falcon Heavy ended up flying on Falcon 9, because Falcon 9's design evolved so much.
It was also better to wait until Falcon 9 boosters could be vertically landed routinely, because Falcon Heavy has 3 of them and that is where most of its potential cost savings come from. Rapid reusability is also an issue: the Falcon Heavy maiden launch used Falcon 9 Block 4 boosters, but all subsequent ones will use Block 5, the "final" Falcon 9.
Falcon Heavy is a fun launcher but it will be made completely obsolete by BFR.