A lot of what I'll be mentioning is a rehash of what most have said, but to summarize what I remember off the top of my head:
In terms of bugs:
1. Weather and advanced strategy - especially qualifying on a track that's under changing weather; very easy to find a mix of wet and dry compounds for both qualy and race without the manager intending for those tyres, for example qualifying on Inters when you had chosen the faster Dries in setup, or starting on Dries when the rain has already started and when most of the grid is on Inters or Wets.
2. Track bugs: for example lap 3 DRS in Spain, or strange lines on the first lap of Eur which cause the pole sitter there to almost always lose the position come the first corner.
3. Occasional glitches in the system whether it be race schedule or race start time going wonky, investment/engines/parts purchases not going through (personally never had this issue, but seems to be reported occasionally), game getting stuck in "go to race" after the race has finished (some leagues face this issue, others don't)
4. Graphical glitches: cars jumping around, boost or DRS icon still showing even after they've been closed. Doesn't happen often but when it does, it could be a thorn on the eyes.
Thankfully we've long been rid of things like the autopit bug, where most managers would have the pit in button flash 1 lap before their scheduled pit; used to claim lots of managers back in the day.
Rather than talking about technical variables or aesthetics, as I believe others would be more comprehensive on those, one improvement to the game I think could help would be:
1. Better league search and league customisation. I used to bring league search up ages ago. Make it easier for managers to find leagues using the league search function, allowing them to sort by more filters such as:
- Race speed, race distance
- activity in league (no. of managers in league). It would even be a neat option to have fully occupied leagues be shown should managers check the option to do so.
- average reputation
- more that I might remember later
On league customisation, I appreciate the effort lately to give more functions to league hosts and league members, from the reply function to the welcome message and league message features. However judging from demand, I think most managers would be even more satisfied if we had options to:
- have custom league rules, especially a tyre compound rule for leagues who'd want to run one.
- custom race schedule; don't have to have all the 17 races in one season. Able to switch races around, etc.
- There could be more fun things like whether all managers in the league would start the season with regular base design or something like 1 base design the next season for all managers. Different points systems too.
I may remember more bugs/ideas eventually, but I'll end this post here.