Like what? I find 5e (minus the newer, ridiculous stuff) is great for beginners/kids, but not crunchy enough for more advanced and/or older players. That's one of the reasons I started building my own system. I'm curious to know what layers you've built and how they would coincide with the layers I've built into my system.
To be completely transparent, very few of the mechanics are entirely my own. I have A LOT of D&D content that I've poured over to take the elements that I like, tweak, and put them together in one document.
Some examples are:
1. Greatly expanded the skill system to include additional tiers above proficient for all characters and skills (Expert and Master) along with Sub-Skills which are basically specializations. E.g. Pick Pocket is a sub-skill of Sleight of Hand. I don't have a master list of sub-skills. I allow the players to choose them as part of character creation to really help them flesh out their character. It gives them an opportunity to pin down what they're really good at. The system is hit/miss. Some players are lazy or morons and it does nothing for them. Others are creative and inspired and it's a meaningful addition.
2. Crafting. Far too many details to post.
3. Gathering and harvesting resources from the world and monsters. Same as #2.
4. Fame/Infamy system.
5. Upgrade paths for normal weapons and armor (via properties). RAW, you buy your weapons/armor at character creation and after that it's magic items or bust.
6. Stacking Advantage/Disadvantage system. You never get more than two dice either way, but each additional source count as +/- 1 (+/- 3 max) and counteract each other at a 1 for 1 ratio.
7. Running businesses, kingdoms, settlements, etc.
8. Pages after page of smaller but impactful changes like all weapons and armor have a minimum STR requirement, 2 levels of Exhaustion when you're taken to 0 hp, re-vamped rest system, etc.
Players that join my game get a 65 page pdf of my house rules. It continues to grow as I test. Some things haven't worked and some rules are voted on by the group because certain things like gear maintenance, lingering injuries, etc. are loved by some and hated by others.
I exclusively play on FG now, but I had an
extremely difficult time transitioning from tabletop to online. I honestly don't know why (apart from Fantasy Grounds having a pretty steep learning curve), but everything just felt very foreign and I underestimated how much I needed to non-verbal feedback I got from players. It took me several months to get my feet under me, but things run really well now.