The devs have chosen, strangely, to make certain keys function differently between legacy mode and standard mode, rather than maintaining key functionality but just removing standard mode's camera snap. If you change these keybinds so that your keyboard uses the same keys in legacy that you would have used in standard, you might find it fixes any perceived issues you have with legacy mode so that you can use it all the time.
Code:
Key Standard Legacy
=== ========================== ==========================
W Move Forward Move Forward
S Move Back / Walk Backwards Move Back / Walk Backwards
Q Strafe Left Move Left / Turn Left
E Strafe Right Move Right / Turn Right
A Move Left / Turn Left Point Camera to the Left
D Move Right / Turn Right Point Camera to the Right
If you rebind your keys so that Legacy's Move [Left|Right] keys are the keys you were using for standard Strafe, and you bind Legacy's Point Camera [Left|Right] keys to use the keys you were using for standard Move [Left|Right], your legacy movement will become "standard movement, but you never backpedal and the camera never snaps in a disorienting way".