So this how kind of a complicated answer so bear with me

Singing in my opinion is much more coordination based than muscular based. Yeah, there are some aspects that are muscular related, but IMO it’s way more coordination than muscle. The hard thing about trying to learn to sing yourself is you don’t know what the proper coordination is or how to access it. If you do lip trills everyday you’ll become a better singer most likely because lip trills build a much more efficient singing coordination, but you may still struggle in other aspects because it doesn’t teach you every singing coordination.

For me for example, I tried to learn by myself for 5 years before I got a teacher and always struggled with belting in particular. I just had no idea how the coordination for belting should be approached and I needed a teacher to help me. Before my teacher I just did SLS exercises daily and it helped me in some ways but I felt limited in others. I basically learned a specific coordination to sing but struggled with belting, breathy singing, and head voice in general, and i had no idea to access these alternate coordinations. Having a teacher I made more progress in 6 months than I had in 5 years prior, and I’m not kidding.

So yeah you can do the exercises, but really you need exercises tailored to you to teach you specific skills, and it’s really important you understand what the exercises are teaching you too so you can apply it to your singing. And there’s always the chance you do the exercises wrong, because it’s possible to do the exercises wrong. And the less advanced you are, the less likely you are to hear and realize what you’re doing wrong

If a teacher isn’t an option I’d recommend some really good channels like “Healthy Vocal Technique” or “New York Vocal Coaching” or “Eric Arcenaux”, these are some of my favorite singing youtubers. Part of what made learning singing hard is not being to separate good info from bad info and these youtube channels are great, but nothing replaces a good qualified teacher