One thing you could do would be to mark the old investing accounts as Separate and Hidden. That way the data will still be in your file in case you want to refer to it but it will not affect your reports and net worth.
To do this, click on the gear at the top right of each account and select Edit Account Details. Check all 3 boxes on the Display Options tab. If the accounts are set up for downloading, go to the Online Services tab and disable them. I do not close accounts because that is irreversible.
Then you would create new accounts for your current brokerages.
You can hide any Categories you no longer use. I would not delete them if they have any transactions that use them, because then those trnsactions will become uncategorized.
Did you continue to update your bank and credit card accounts during the time frame where you didn't update the investment accounts in Quicken? Is there a huge gap in transactions between then and today for all your accounts? If there is, it might be best to abandon the current Quicken file and start with a fresh new Quicken data file as of 12/31/2022 and only load transactions for this year (To start a new file select File Menu / New Quicken file)
Will you be tracking these accounts manually or downloading transactions?
If downloading, Quicken will download transactions as far back as the brokerage supports, then create Placeholders to force the current share balances to match the online account.
If it is a manual (offline) account, the account setup lets you specify what the initial holdings are, usually as of your last statement, and it will create Placeholders to match. With Placeholders, you can go back later on and add the missing transactions.
We can discuss Placeholders separately if you want.
A FWIW comment —
I am not a fan of the Separate account designation. It is certainly not part of my normal setup or operation. Instead of that direction, I would be more inclined to simply Remove all securities and cash taking the account(s) to $0 value. Choose a date that fits your needs.
The primary difference I think is that this way looking back in your history when the data was reasonably reliable, you'll be seeing those accounts as yours rather than Separate. Overall a small thing and a matter of personal preference.