ok let's talk about the #1 issue: players can't claim their builds if they're a clan member, and everyone gets griefed because it's a cracked server.
For good reason, some of the most popular spigot plugins are griefprevention and coreprotect. They have had years of development, and their involved user base helps keep them up to date with the latest minecraft versions. Griefprevention makes both user and server grief a lot harder. Among other things, coreprotect lets operators revert any and all changes, and even store block logging data in another location.
Now let's talk about grief theories and how they affect operators' behavior.
Theoretically, a user could create a claim, use a tnt duping machine, and then move their claim. As a game exploit that mojang frequently fixes, I don't see a problem with disabling tnt duping via plugin, namely a plugin that goes by the name "illegalStack" that receives active development and resolves dozens of server-breaking behaviors like afk fish farms, tnt, duping, rail duping, hopper stack duping, etc. In combination with griefprevention, the probability of grief (where admins would normally need to intervene) drops closer to 0%.
Because users often theorize that "redstone == lag", operators have done their best to break the game via hopper settings and redstone clock blockers. There are existing plugins that provide feedback on how much of each server tick is spent on different tasks and offer ways to boost performance in ways not noticeable to players. Some changes, like mob stacking, are VERY noticeable and ruin the game when it doesn't work the way it should.
A very real source of lag would be growth ticks. Letting players farm through /shop encourages excessive farming behavior that harms the server.
Now let's talk about another basic problem set surrounding jobs and /shop.
First of all, the goal behind a jobs setup is to encourage a variety of players to work together through different tasks. Using multiple jobs as a source of income for /shop accomplishes the opposite. /shop is buggy and unnecessary and detracts from the "multiplayer" elements of "survival multiplayer". This is why /shop is generally considered by experienced and friendly players (i.e. most donators) as a bad idea for a community-driven gamemode. The easiest way to improve the game and encourage donations would be to simply not set up /shop and set jobs to give exp rewards in place of the plugin's point system and use "quests" to earn rewards relevant to the trade.
Now let's talk about the general lack of content.
1.13+ allows the use of datapacks to modify loot tables, add recipes, and create functions. I'm personally a big fan of tyuswoo's game-changer datapack, which uses functions to change mobs on spawn event and generate structures at runtime (which requires extra performance). It's a good reference of what's possible with the new options available. Of all the options available, we got nothing unique. I wouldn't even mention this lack of content if I didn't need to back up the fact that the development of the latest survival release seemed lazy despite how easy it is to put together a decent survival server.
Bugs and suggestions are being ignored since there's almost nobody among staff that knows what's going on or what to do about it. I tried to volunteer to help, and my application was met with unnecessary hostility over a simple mistake regarding the fine print at the bottom.