More work needs done to the server. (A Lot)

The issue is that, we run heavily modded minecraft servers and they can not be compared to vanilla minecraft, mini game servers or even pixelmon.
A server with a lot of mods, many players and progress never runs smooth, that's just how it is. Out in the world of modded minecraft servers we are running one of the most stable and well performing servers there are, if not the best (and I'm not saying that purely based on believe, we have a lot of ex-staff from other networks joining us from time to time and lay out some comparison)

Of course there is always room for improvement and if we would stick with a single modpack or even server, a lot more work could be put into that one with our size. But please don't forget that this usually means that the team would be way smaller, too. Further more, we might never match the stability and performance we have with our current setup. I know this doesn't sound logical but there is a mind f*** (paradox) behind it. In order for us to be able to fix stability issues and performance leaks, we need extreme cases. Extreme cases make it a lot simpler to find the source and also make it way more important to fix it in a timely manner. Now most of these under the hood issues require certain circumstances to appear in an extreme or even noticeable state. If we match 20 players, one server and one modpack against 250 players, 30 servers and 14 modpacks, that is a difference like day and night. As you need to multiply all factors.

To give you an example, we once had an issue with galactic science, the server was hit very very hard by it (couldn't handle even one player). This pulled our entire focus on that one server/modpack and we spent days trying to figure out what the actual source was and later on building a solution. Once we had that, galactic science was back on and players could continue their journey. But this was only a very small part of the benefit it gave us. Once we started deploying the fix on other servers/modpacks (which all didn't have this issue, at least not noticeable), all those packs/servers gained a performance boost in a two digit range, which is insane. Especially as the performance issue wasn't visible, even with proper profiling.

Now if we would not have had a galactic science server, all our 1.7.10 servers would perform way worse.

This is just one example from many such situations.

I hope I could give you some insight and make you notice that its not all black and white. It is always important to look for as many puzzle pieces as possible, the less you see, the more the unforeseen effects hits you, as we can never see all the effects of our actions.