Don’t Think of Reverb Acoustically
The first thing you can do is stop thinking of reverb as a ramification of physics.
Don't think of using reverb as an acoustic effect. Think about using it as an emotional effect, or a narrative effect. Lyrically, is the song set in the present or the past, or is it perhaps in both? Can reverb be used to differentiate the past from the present, or the present from the future? What does the past sound like? Is the future wet or dry? When the singer is in their head, what does that sound like? What is the reverb of thoughts?
Is the character in different spaces during the song? Is there a bedroom, or a kitchen? Is the character in one place during the verse and another place during the chorus? This might be something you decide that's not based on the lyrics. It can just be a decision you make.
Control the sense of space and intimacy. Reverb is distance. Want a vocal part to sound like it's in the listeners' ear? Dry it up and pan it hard. Control the depth of the soundstage by putting some things farther away than others. What's in the back of the room? What's in your face? Make decisions, damnit!
The listener probably will never go, "Ah, the singer is in the bedroom in their past, then dreams they're in a canyon, then they yell in a bathroom." And honestly, you don't want your listener noticing all that stuff, that would be like watching an old Godzilla movie hoping to see the strings moving everything. But you do want your listener to "lose" themself in the song, and you do that with small, well-thought out decisions. It's like when you eat food prepared by an excellent chef. You don't know what little tricks they're up to. You're not thinking, "Ah, this butter has had the solids removed so it is actually closer to ghee." You're just thinking, "Man, this is delicious."
We want people to hear the results of our work, not retrace our exact steps. We're not making records for other engineers to like.
Put two different reverbs on two channels and pan them so that one reverb is on the left, the other on the right. Then, feed the signal that you want reverb on to channels, or more one than the other - whatever you want. The more different the two reverbs are, the weirder this effect gets. A short decay time on the left and a long decay time on the right will move the reverb across the speakers from left to right. There are all sorts of things you can do with this set-up.
Set really long pre-delay times. Pre-delay corresponds to how close the nearest wall is in a space. In a small space, the nearest wall is only a few feet away, but in an aircraft hangar, the nearest wall might be hundreds of feet away, so there will be a long pause between the direct sound and the start of the reverberant sound. Our ear makes decisions about the kind of space it is in based on when it hears the initial return of the room, ie., the pre-delay. So, a small room with a huge pre-delay sounds very unnatural, as does a huge room with a very short pre-delay. This is a fun thing to experiment with; it adds a bit of "acoustic confusion" into the mix. Perhaps tie the use of it into the lyrical or emotional content of the song. Like, the singer is expressing doubt or confusion in a section, and to heighten that, add a short reverb with a long pre-delay, which not only pops the lyrics out but also gives the listener a hint of confusion.
Compress your reverb returns. Stick a compressor on the insert of the return channel and squash that stuff. Play with the attack and release. Can you get the reverb to "breathe" along with the tempo of the track? Long attacks will increase the "punch" of the reverb. Short attacks and releases can lend an almost backwards sound to the reverb. Experiment with putting the compressor both before and after the reverb in the insert — you'll get wildly different results.
Duck your reverb returns. Put a compressor on the return (you pick the spot in the insert chain) and then key that compressor to duck the reverb. If you key the compressor off, say, the vocal you're putting reverb on, you'll get a very clear vocal with reverb blossoming whenever the singing stops, and there's no automation needed. What about ducking the backing vocal reverb with the lead vocal, especially if there is an alternating quality to the two parts? You can also key reverbs off percussion so that the kick or the snare stops the reverb for a moment, which can give you all sorts of rhythmic effects in addition to giving your mix clarity. Remember, reverb tends to muddy things up, so if you're ducking during busier sections of the song, you're going to increase clarity in those sections, and differ the effect of the reverb 'til a moment after, so the track will be clean but still have an overall wet quality.
Gate and Key your reverb returns. Gated reverb is a staple effect on drums from the late 70s, to the point where it is a cliché, but gating a reverb and then keying it from another sound source is still a fun thing with which to experiment. Key percussion with itself to get a classic gated reverb effect on something other than a snare. Gate the reverb of a tambourine with the snare so there's a huge wet noise on the snare that isn't the snare. Gently expand (a gate that only reduces output by a few dB, such that when the gate opens there's only a slight volume increase) the tails and decays of pads with the rhythm instruments to extend the feel of the groove into other aspects of the sonic landscape.
Modulate your reverbs. It's amazing how cool a little chorus or phase sounds on reverb, and how people seldom think to do something so simple and effective. In the old days when hardware units were the only option, it was hard to sacrifice something like a rackmount flanger to a reverb, but nowadays, just throw a plug-in on it. Just experiment. Like a lot of effects, modulated reverb is best used sparingly, to heighten a specific moment of a song, rather than having it on all the time. But rules and suggestions are made for breaking and ignoring, so feel free to slop modulation all over the place, but perhaps control it with ducking? Modulated reverb on strings, keyboard pads and chorussy vocals can add an otherworldly effect to things, and you can reign it in using keying and automation.
Goof Around in Fadeouts. Good fadeouts are an art form. I love fadeouts that have a little something in them to catch your ear and pull your attention back into the song. An amazing, fast guitar run, a spectacular vocal moment, someone talking, etc. Doing wacky things with the reverb in a fadeout is always fun. Crank the reverbs up so that things sound like they're going farther away as they fade, or dry things up totally so that the fade makes things sound like they're getting smaller. Roll off the bass gradually and pan things tighter to accentuate the smallness.
A last bit of advice: you’ve got more power in your laptop than anyone in the studio biz has ever had. By next year, that will probably double. Put that power to use in the search for something new, different and yours. Experiment and play. Don’t let Ai have all the fun.