National Rail Journey Planner allows the route via Liverpool St. It uses the Elizabeth Line, but there's lots of greyed out options because of current disruption, so not sure what other possibilities it might suggest!Out of interest, if you purchase something like this, could you still change at Stratford and head to Liverpool Street? Is that still a permitted route, given you wouldn't be travelling on a Gravesend to London Terminals ticket?
Buying a ticket to somewhere you're not going is often an adventurous path to savings. And you still have the option to continue on to where you weren't going if you have some spare explorey time!!