Not every group is going to be a top-tier group, no, but like
@RandAlThor said with Dreamnote, plenty of groups settle into a comfortable mid-tier existence with consistent, if lower-budget, comebacks. Look at DIA for example---they had pretty consistent comebacks for five of their seven years, although MBK did screw the pooch with their 2021 comeback that never came to fruition. My ults Verivery also count. They've had their fair share of viral moments and have had some songs perform well, plus hype from B2P and RTK, and they're comfortably mid-tier enough to get comebacks and a member's solo debut recently, with the members planning for further comebacks. Granted Jellyfish also screwed up a bit on that by not giving them any new music from mid-2023 to late 2025, but kept the members performing during that time to keep the fandom at least slightly fed. But then, what K-pop company doesn't screw their idols up at least a little bit?
I agree. Smaller companies should for sure do all those things. I also am a big fan of involving the actual idols into their very craft, be it writing songs, composing, instruments, or if some are gifted in that sense make them design outfits even or atleast be involved in it.
As you said, by MCing, or appearing on YT shows, it can boost the group their popularity too which is exactly what they need. I think shows where idols can be themselves is also something fans really love and attract more people. Idols already have a hard time for being lived through their company, so often non fans will view them as fake by default.
I think this can be really useful, not just to make the idols' music more authentic, but to help them put out music if they have less popularity to where their company is constantly pushing for a comeback. For Verivery's latest group comeback, all three tracks were co-written by the members and from what I remember of their lives at the time it sounded like the members had a lot of hand in putting the album together. If the company isn't going to invest in them as much it's on the members to deliver if they want to have a comeback, so having members that know how to do that is important.
even less can toy around like Red Velvet and essentially build 2 separate fanbases.
I think some less popular groups can do that---I remember back when I was on Verrer Twitter, there was basically half the fandom that were "bright concept Verrers" and half that were "dark concept Verrers". You just need some sort of common sound or something linking it together and a strong group personality. Verivery's music has always had the common thread of having prominent melodies no matter what genre they've tried (except GBTB, but it's the least popular among the fandom for a reason) when a lot of other groups don't have that. You also have to keep both sides fed, hence bright TTs with dark bsides or vice versa. And then I believe as a group when they interact and such, they have very strong personalities that keep fans interested.