Stepnix

If you still want a fantasyish game but your main issue is that the mechanics are kind of fucking boring, well, that's the 5E experience. I recommend giving 13th Age a look if you want to get more loosey-goosey with things like better supported theater of the mind combat options and more PC control over the narrative with things like One Unique Thing or relationship dice (look up a PDF, one of the authors sucks balls, don't give him money). You can also check out Pathfinder 2E if you want to get firmer on things. In both cases their full SRD is online free and pretty easy to google. (Or, and here comes the product placement, take a walk on the indie side.)

This is of course assuming you want a fantasyish game. If not, do you have any idea what you might looking for?

If moving away from Tolkien-adjacent fantasy is in the cards, I would recommend Blades in the Dark. It's absolutely a game about it's setting, which I'm told is very Dishonored-coded (I've never played Dishonored, but the vibe looks right from the screenshots of it I've seen). It's game about being a daring criminal gang in a haunted Victorian gaslamp city powered by demon whale oil under a veil of perpetual night. It even has legally distinct tieflings.

In regards to GMing, it has much more reasonable prep volumes compared to DnD, imo. Most of the prep is moving the factions in the background in response to their agendas or the player's actions from their last job and thinking up a few leads for their next one in case they don't have any ideas of their own to pursue.

if you're at all interested in magical girls or grid combat, Princess Wing will serve you very well for one-shots and short campaigns. It's very different from a lot of other TTRPGs, and somewhat more "scripted," but imo that will help you stay flexible and get better at recognizing what different systems ask of you

https://cohost.org/Fel-Temp-Reparatio/post/2778522-you-ever-wish-you-co

CAIN, demon hunter TTRPG from the author of Kill Six Billion Demons, is very stylish and made for relatively short campaigns

For games that are a blast to play as games, LANCER and things inspired by it rule. The combat mechanics give a good variety of options, and each mech is so customizable based on how you level up (which happens after every mission, so win or lose players still get something to play with). This leaves a lot of out of combat stuff to be desired, but the Karrakin Trade Baronies expansion adds more out of combat stuff and like, Personality Powers.

LANCER is nice because the level cap is like... 12. I wrapped a game after 9 missions or so.

ICON is similar in that it's about tactical combat like LANCER, but it's fantasy based and has more out of combat rules at the jump. It has a ton of cool classes though, and is currently free because it's in beta.

The most fun mechanics-and-fiction-working-together game I know is Masks: A New Generation, which also happens to be a relatively easy to pick-up-and-play PBTA game. If I needed to GM something (not GMless) at the drop of the hat, it'd be that.

If I wanted a change of pace to lead a group in something without a GM per se with some engaging mechanics but no rolling, I think I'm sorry did you say street magic would be high on the list (played either in one or across multiple sessions). It works at multiple levels of familiarity-with-indie-games, and you can even sell it as "let's make a setting to play our next 10-session campaign of (whatever system) in", if players are skeptical; once they start playing, they'll find it fun on its own, too.

If I needed to GM something close to 5e, I'd run Pathfinder 2e using the Foundry VTT that carries most of the rules weight. Someone at the table needs to know the rules in the abstract, but it's pretty impressive how much of the stuff can be searched or surfaced (or made into macros with 0 research) within the VTT.

i had a lot of success running old school d&d for my playgroup. we started with shadowdark (new publication), moved to old school essentials (reformatting of 1981 d&d), then settled on AD&D 1e (my peculiar fascination). all three were successes in their own way; the osr space is worth investigating if you are looking for d&d-but-with-more-engagement. people tend to get very involved when stakes are high and treasure is important.

ad&d is not a good choice for simplicity, but OSE and shadowdark are. shadowdark has some similarity to 5e mechanically so you would be at home there.

The easiest-to-pick-up are probably the firebrands lineage of games. You have mech scifi in MFZ: Firebrands, you have fantasy in The King Is Dead, you have goblin pokitics in Gobless Oblige, magical girls in For The Honor. And a bunch of others in the rhymerbrands jam on itch.

They're probably not the most exciting as game systems, but I love them for being strongly guided conversations.

Alternatively, have you considered a different physicality? Dread, Star Crossed and my own Tensile Breakdown use jenga towers as resolution tools for horror, romcoms and sad mech fights, respectively.