I would disagree.On the contrary , more Air and Sea assets are what needed to get on the island , consider how overwhelming the US were compared to the Japanese at 1945 , but even them decided that taking the island even without a rebellious local population was too costly .
Both parts of this operation will be hard , landing on it , holding it , both would require overwhelming and constant , air and sea dominance.
Consider about 30% Coalition sorties in the fist gulf war went for the SEAD operation alone and still yet had planes shot down, I don't think that it can be determined that PLAAF is has the capability to do so against a better equipped and prepared enemy, and with PLAAF lacking the constitutional knowledge to do so , the bigger the scale the air operation will be , the bigger the gap between PLAAF and USAF.
The same goes to the rest , the Allies during ww2 had more then 1 landing to learn , before attempting the most complicated military operation to date , and PLA will need to succeed in one that is both bigger , and more difficult .
So is getting on the island and staying there .
Broadly speaking, I think the PLAAF has enough assets for air superiority. However, it could do with more drones and precision guided munitions for existing platforms. That does not require a large increase in spending.
In terms of the PLAN, there are sufficient surface naval ships to achieve maritime supremacy. Again, there are niche areas where the PLAN needs more capability like minesweepers and LSTs, but these are not expensive ships that require a large increase in spending.
In terms of SEAD, I see Taiwan as being easier than Desert Storm due to improvements in technology.
A staff officer for the PLAN who worked on the 1996 Taiwan crisis said that in order to hold the beach head , they need to be able to land a full brigade in the first hour , and a full crop in the first day to have a good chance of winning , and back then , it would be impossible even if all ships that was available to the navy was put into this operation , even today , with all of the landing crafts PLA has, it lacks the supply ability to maintain a group army on the island without capturing a port .
( I will link you if I can find it )
I think fundamentally you are underestimating how difficult a cross channel invasion is , it was , and still is , the most complected operation type of conversional warfare , and given the population size and how well equipped Taiwan is , I don't think it will be a exaggerating to say that an successful invasion of Taiwan that is willing to fight , will be the most difficult operation every carried out by any military , and we cannot assume that Taiwan doesn't have the will to do so.
So in my opinion , significantly more PLAAF and PLAN assets , training is precisely what a invasion of Taiwan will need.
We recently went through the logistics for a Taiwan invasion in the relevant thread already. By my count, PLAN amphibious ships have capacity for somewhere between 1400-2300 vehicles. 1400 vehicles would correspond to the ground combat vehicles of 4 Amphibious Brigades.