Can I amend my 2021 return and use my 2019 instead since I made more?

Do you mean for EIC purposes?  But note that higher income does not necessarily translate into higher EIC.

You can amend your 2021 tax return to use your 2019 earned income if it will benefit you with regards to your earned income tax credit. 

You can file an amended return using TurboTax for no additional fee. You will see the option on your Home Page in TurboTax, then under Your tax returns and documents, look for an option to Amend/Change your return. You should wait until you receive your refund or the IRS has processed your return, if you sent a payment, before you amend your tax return.