I spoke about Meatier using the past.

well-supported Rethink package

At the end, Rehtink has been having a lot of serious issues that pg addressed better.

Meteor is built in Node 4

and has trapped users in an old version of node for long. Also, 4 is not in active LTS anymore.

CSS modules are available

Everything that merge the front and the back will eventually suffer a scaling limit.

the best pre-built stack for the job

That does not exist, you always end up changing what yo want to do to do it with the stack you have chosen or to abuselly hack the tools you use. Truste me, when you have to maintain old projects, it is a terrible pain.

I'll just think you're wrong.

I'm surprise.

you'd need to implement DDP

DDP is not needed, you just don't need that.

syncing of a frontend database and your backend database using database diffs

There are countless solutions to this problem.

I can honestly say I've never heard of anyone doing anything like that from scratch with fewer than 100 engineers.

Then you probably have met nobody talented or even just have never open your eyes ever.

I wouldn't call myself an expert

Good for you.

I wouldn't be able to do from scratch with 5 of me.

Then you need to think about another career path.