As a HoS main, and antag player, I might have a bit of insight into this. It's something I reflect on a lot when we are discussing gimmicks, and too when I try to respond to antags on station. Disclaimer, due to this I will mainly be talking about the security-antag dynamic, as in my opinion- this dynamic is the driver for a majority of roleplay actions on the server. Explosions requiring repair, Surgeons fixing ribcages all flow back through the sec-antag dynamic. Firstly, I think it is a lack of creativity. Creative gimmicks are shot down in favor of gimmicks that require less lore knowledge or adapt skillsets.
Consistently while antagging, unique and insightful gimmicks are shot down due to complexity. A skilled antag who can perform a good gimmick will be outvoted for a mediocre gimmick that requires very little lore knowledge or additional effort to maintain a gag. This issue of nonunique gimmicks compound when you consider people play archetypes. Certain gamemodes lend themselves to specific gimmicks, and when there is no originality or originality is outvoted due to the issue above, you will see a 'rut' of the same gimmick being played over and over. Which is the second issue- the same gimmicks are presented over and over.
When you have the first issue resulting in the same gimmicks being played over and over, people, especially security, get tired of them. No longer is it a freeform roleplay experience, but a rehearsed and choreographed dance that occurs. When the gimmick is repeatable, so too are the responses. If you were to supply a 'round equation' for each popular gimmick, a majority of those gametypes would follow the average equation. Only semi-often does the gametype break from the gimmick mold. It is the responsibility of both the security department as well as the antags to introduce uniqueness. Uniqueness not only in gimmick or antag actions, but also in response to them. The latter is hard. Antag failure to involve other deparments vs. mentality of 'play vs. security' is a hinderance as well.
The latter, response to gimmicks, is especially harder for peace-antags.
A peaceful antag forces security into fewer choices of response. Upon verification with central command, if CC goes with the gimmick, security will almost surely be completely pacified. The peace-antag is then wholly responsible for driving narrative for the gimmick, involving the other departments / full station as they wish.
How many rounds have you witnessed where an peace-antag, say, a healing wizard, joins, is granted amnesty, and is merely monitored? They then join medical, and just become another surgeon with some magical powers. Perhaps they visit the bar? This is driving narrative at a turtle pace and is in no way entertaining after the 10th time you have witnessed such a round. What is the solution?
I'm not certain, but a wise man once said do not complain unless you have a solution. So- in addition to the 2 cents of advice above I will say this;
I believe that the dynamic gamemode intensity PR is going to resolve a lot of this. Introducing randomized sets of antagonists and different 'difficulty' levels will allow for new combinations that we have yet to see. Yes, we will still have classic combinations, but I believe that the playbooks will have to be set aside for some of the new combinations. This will improve gimmicks.
Additionally, and this is a point that is contested and is purely my opinion-- security's use of force escalation has been messed with. I think it should be looked at.