First, they lose economic leverage, so the US can sanction them, turn them into a pariah. They don't have an India to rescue them, like what happened with Russia. All other Chinese friends are too poor and useless to help them.
Second, the US is still a much stronger country militarily. Even if the Chinese build more assets, they still need 15 more years to catch up. So their production advantage is much further into the future. Right now, they moved first, so their military capabilities within the Taiwan theater is superior, but that will change once the US introduces new ships and other capabilities, like AB Flight III, upgraded F-22, mature F-35, hypersonic weapons etc. They are also improving their intelligence infrastructure drastically. 4-5 years from now is enough time to nullify a lot of the advantages the Chinese are expected to have by 2025.
Third, delaying the invasion will give Taiwan more time to prepare. The Taiwanese are developing capabilities that will help them hit targets deep within China. They are currently building 500 missiles a year and will climb to 1000 next year. The more time the Chinese take, the greater damage their ports and other infrastructure will take. And this doesn't include foreign supplies.
Taiwan is very rapidly building 2 submarines with Japanese and American help, apart from operating 2 other upgraded subs. So they will have at least 3 or 4 subs before 2026 for shallow water operations. Plus any war with Taiwan will see Japanese participation. So the combined US, Japan and Taiwanese fleets are bigger and more advanced than the Chinese one. We will naturally see the involvement of the UK and Australia as well.
So the Chinese only have until 2027, post which the next opportunity is unlikely to come for many decades. And their declining birth rate is not helping matters. And any attempt to reverse it will bear fruit only a decade or more later.
