Hello, there friend!
Have you been drinking the kool-aid? LOL
I think you've been here too long and are getting freaked out by all the kids wanting to know theory or should they know theory, and what are the notes of this scale or that scale? and if you are missing something important.
I think you have probably heard one or two of my youtubes by now.....
And you can be the judge of whether my solos are decent enough....
What I know of theory could fit on the head of a pin. All I know is a few box patterns for a few scale modes and where the notes on the fretboard are and how they link together up and down the strings and frets.
That and lots of practice and lots of listening to great guitarists for years and trying to learn what they played and trying to emulate it in some fashion.
That and a fairly "musical" mind.
Almost all my solos are improvised and are never the same. Some are complete failures. Some work out great. The majority of the recordings I have are the result of many takes in which mistakes were made and ideas were formed and elaborated upon.
Of course, playing live in front of a crowd where you only have one shot at it is the truest test.
Nowadays, I'm very rusty and have forgotten a lot of what I used to know, but some of my technique has improved with age. But when I was active as a performing musician, I was pretty well honed in the fire.
Adrenaline helps a lot! It can really lend you a motivation and skill you didn't even know you had in you.
Now, I know you are a metal guy....and that could be part of your problem. Metal has it's own challenges as far as how to construct a solo to. I would be an awful metal player. I know very little of tapping and pinch harmonics and sweep picking and all that stuff.
I'm more of a Ritchie Blackmore type player(since he was my template as a teen and I listened to and practiced that style religiously)
John Petrucci I will never be.
Or Dimebag or King or Wylde.
One suggestion I would have for you is to try going back to the roots of rock guitar and checking out and trying to learn what some of the guitar legends of the 70's did. Go back to standard tuning and learn some old style "Heavy Metal" or "Classic Rock"
but learning to solo involves a knowledge of a few patterns and scales and then lots of self discovery until you don't try to "write" a solo before you play it, but feel the music and with the familiarity of doing all that solo noodling, things will just come out of you.
I cannot express HOW I do what I do. It just kind of happens.
Do try and slow down a bit and don't try to fire off "amazing" solos. Instead, try to play a bit slower and more musically.....(again...I know that metal is hard to play slowly. LOL)
The odd timings and speed of metal doesn't lend itself to really feeling a melody of the song and improvising off of it. That to me is the key to soloing. Working off the melody and harmony and fitting within it and elaborating upon it.
Trying combinations of triplets, two note intervals, long single notes and bends, etc, all mixed together.
Two note intervals sounds a lot like pentatonics....Which you may have learned about me, I despise, and believe hampers a lot of young players trying to learn guitar.
but learning to solo is really just a lot of practice playing to backing tracks like Tony said OR best yet, jamming with a friend. That is how I got really good at it. Me and a friend of mine would just have our guitars and would play a simple repetitive rhythm lick, like the long ending of "Freebird". Or the "Comfortably Numb" riff. We would pick a minor scale riff and a major/blues scale riff and then each one we'd play for 20 minutes minimum and trade off rhythm and leads.
That's how you experiment and find out what works and what doesn't. Practicing a certain type of lick or arpeggio...things of that nature.
Blah blah blah....you get the idea....
But only you can determine if you need "lessons" All I know is that taking two months from a good teacher on how to solo REALLY helped me transform after 6-7 years of being self taught.
A Mikey likes to say, get lessons from a professional if you really want to learn guitar. As an adult, you can specify what you want to learn. And if the teacher doesn't know that, find another teacher. Make him show you what you want to know, and don't let him force his own curriculum on you. He works for YOU.
Cheers