150,000 troops participated in D-Day. China has two million troops, and has already unveiled a plan to requisition more than 2,500 large civilian ships to supplement an amphibious assault. Furthermore, China has several thousand short-range ballistic missiles targeted on Taiwan: a weapon that didn't even exist during D-Day.
Except the numbers don't matter much if you can't LAND the troops. Even with the swarms that D-Day used, they were likely close to saturation without stumbling over themselves. Taiwan has far less useable beach and a smaller area than France had exposed. You can also launch a million missiles into Taiwan but that still doesn't mean you can set up a proper beach head to allow the inflow of personnel and materiel.
Even Russia with basically FAVOURABLE land (no water crossing required) has tons of issues toppling Ukraine. China has an even bigger task on hand.