actually,things aren't so easy which one thinks...Amphibious Assault is always one of the most difficult form of Warfare.I'll put it just behind of Airborne Invasion.Success of an Amphibious Invasion lies on several several points.
Objective-- To capture entire Taiwan and make it submission.now,Taiwan's Force isn't weak.it is somewhat good according to its size and truly can defend itself to certain point.
Intelligence
Approach--China may target some unguarded beaches,which may reduce their casualty.but their journey will be none the less perilous.see,Taiwan has a capable Navy.they owns a lot of ASCM.Smaller Crafts armed with ASCM(missile Boats like Kuang Hua VI, which Taiwan has some around 40)could be used by great effectiveness to damage these troop carrying ships.plus,Coastal Arty will be another thing of concern.nobody could expect to wipe out entire "Coastal Battery" using Missiles and Bombing.even 30% of Coastal Arty could be devastating.
Assault--if we look towards the battle plans of Taiwan,they're relying on their Army now to defend their Shoreline and Battle will be fought there.their objective will be denying any space to invading force and if it fails,to hold it along the shoreline with the performing "Counter Attack" with help of Navy and Airforce.now,securing beaches in the face of mobile Arty and SRBM will be one of the major challenge.plus,PLA will need to send tens of thousands,if not hundreds of thousand to just secure this beaches.see,most of the beaches of Taiwan is fortified,which will be tough to secure.its easy to say that "thousands of missiles will completely crush its defence bla bla bla",but Gulf War showed that it doesn't.Enemy could regroup even in the face of overwhelming superiority.plus,Taiwan's most(if not all) Airbases are now have Hardened Bases,just like mainland does.it'll be not so easy to cripple their force effectively within short span of time.
Lodgement---To perform this,they've to completely secure these Beachheads so that reinforcements and equipments can be carried out,which is too hard if your opponent has Long Range Arty,cruise missiles and other weapons which could be used to target Ships and Beach Bombardments.
Breakout--Next stage of war.they've to leave Beach and have to headed for inland.now,if we count some 2.5-3 hundred thousand soldiers which will remain and will have defensive posture,clearing this kind of force will need around 2-3 times more soldiers.
the main problem of Amphibious Warfare is bringing all the equipment and Men needed to perform the war.they'll need dozens of LST,LHD/LPD along with constant air support just to secure the beaches and neutralize the opposing force there.now imagine much larger operations just to bring the force which will head for inland.that'll need so massive number of troop carrying ships and aircrafts which China doesn't possess now.now get an estimate that how many ship will be lost(worst case),and if China could carry out the war even in the face of that kind of loss...
now decide whether it is easy or lil bit difficult.