Why is creating a fully reusable rocket so hard?

for several months wev'e been hoping to introduce a fully reusable launch vehicle that is capable of either RTLS missions or water landing of stage's via airbags and/or parachutes. but is is becoming increasingly obvious that its incredibly hard to achieve full reusability particularly with the first stage. you need enough propellant to fire up the required engines for a soft touchdown, but landing legs are very heavy to lift and require extra thrust when attempting an RTLS. parachutes are hard to use as they can easily autocut if the slightest pressure is applied.

we are still testing methods of reusability