You're thinking of things in terms of how they function rather than the value they provide - from a business value perspective COTS and low-code are identical, its just that low-code used to be GUI desktop apps, now they're GUI web apps.
It's much more than gui web apps, it also includes native mobile apps, headless services, integrations, etc.
And from a business value they're very different: COTS you do not want to modify/adapt to your busines, otherwise you get problems upgrading, etc. Low-code is often used to innovate and differentiate, as a programming layer to quickly change COTS to your business needs.
>COTS you do not want to modify/adapt to your busines
This is redefining a term after the fact to suit marketing needs of the new term - with the except of bespoke solutions, it has always been possible to adapt COTS products - have you not seen SAP? Dynamics? Even Excel is COTS
Yes you can modify SAP, but upgrading then becomes very hard. Many companies are stuck at old versions of SAP because upgrading it, including migrating all the customizations, is very expensive and takes a lot of time.
I would consider Excel a no-code/low-code (pretty complex macros in there + vba) platform.
It isn't at all. Salesforce and Netsuite for example don't offer you the option of getting left behind. They might break you, and you can postpone some upgrades/migrations, but not forever.
