Yes, you can still file a 2023 tax return, although you can't do it online. You will need to buy a copy of Turbotax 2023 on CD or as a downloadable file, either from Intuit or from a reliable third party vendor that still sells the 2023 version. You will also have to print and mail your return, since you can't e-file prior year returns.
(Remember, turbotax online can only prepare a 2024 return. Don't try and prepare a 2023 return or add your 2023 information to your 2024 return.)
If you owe taxes and file late, the penalty is 5% of the amount you owe for the first 5 months, and then about 1% penalty plus interest per month after that. However, if you are expecting a refund, there is no penalty for filing late in most cases.
It is a big deal if you don't file and the IRS catches this omission. It is not particularly a big deal if you catch the omission yourself and then file late. If you catch the omission and file late, you will only pay interest and penalties. If they catch the omission and esp if large sums of money are involved, then consequences can be far more serious.