Merge JSON data inside dynamic PDF templates

Question

My problem is rather simple:

I need a tool to merge some medium complex JSON input data inside a template PDF.
Then based on the data:
Some sections of the template could be replicated.
Some sections may be deleted and the gap created should disappear.
Tables could be filled by N elements without messing the formatting.
Tables could have "merged cells inside"

Also templates should be easily adjustable without re-writing the code, this means they could be: editable PDF, Word files, Spreadsheets, some tool's templates... (..html?)

In all the tools i tried (a lot! :(( ), one or more of the points above was always a nightmare.

So far i tried:

• latex -> pdflatex -> pdf: this probably simply reduced my life expectation by 1.. 1 and a 1/2 years. Unfortunately the most powerful tool because.. Latex? anyway not maintainable at all
• pdfminer\pdfjs\whatever npm pkg.. : coding always ends up in a low level mess or huge workarounds.
• google sheets -> pdf: APIs are kind of hard, and anyway are cell\row based so it's difficult to manage dynamic sections
• pdfgeneratorapi.com : basically what i needed with a rich editor in it, but formatting and aligning tables is bugged so results are always ugly. Also things like "merged cells" are not possible.

So question would be: is there a tool or package out there in 2022 capable of handling all these requirements at once?