I have a very old store that has been through hell, it's basically held together with duct tape. It started life as magento 1.7 then went through upgrades, dozens of extensions installed and uninstalled, custom templates that add "tools" to the magento backend. I made a copy on a development server and tried to upgrade it to 2.2 or 2.3 version of magento with no luck.
Now I'm trying something new. I installed a brand new version of Magento 2.3.3 on the development server, and I'd like to bring in my customer data, my orders, and my products into it. I'm going to be making a new theme, and I'm fine with reconfiguring everything from scratch. I'd just like to keep the close to 10 years of customer info and products.
10 years built customers info and products is huge I see. But you didn't share how you manage to handle the data transfer using system tool. Experienced is what I see in your business on Magento. But if you are yet proficient in upgrading to later versions, I suggest you look out for help from freelance developers or reputable apps/tools. You can direct message me or visit my profile for more specific solutions.
Installing brand new and latest version of a Magento store and then transferring data from the old store has become a common upgrading method recently. Still, you need to find a solution which can handle the task securely and accurately. You can look up for a shopping cart migration expert or view my profile for some specific names
WKR
We've been upgrading our clients' platforms from 2.1.x to 2.3.3. The way we do it is we upgrade the platform to 2.2.9 first via composer update, run bin/magento s:u, then we fix any error that show up, then we upgrade to 2.3.3 via composer update, run di:compile, fix any error during that process, usually from custom work we did, then finally static content deploy, and fix error from it. In the process we had to remove a lot of third party modules that are no longer compatible, revert the checkout from the one we used to default magento 2 checkout, fix any custom work we did so it will be compatible with magento 2.3.3, etc.
Experienced is the thing that I find in your business on Magento. However, on the off chance that you are yet capable in moving up to later forms, I recommend you pay special mind to help from independent engineers or respectable applications/devices. You can coordinate message me or visit my profile for more explicit arrangements.