I LOVE people with bad teeth! ;-)
Seriously, if you have extensive dentistry over a period of years and
things continue to break down, something should have been done to look
into why this is happening.  Some people are prone to decay, periodontal
disease etc., but there are usually mitigating factors under the control
of the patient and dentist to make the overall situation better or
worse.  If all these avenues have been explored with no success--I am
sorry.  But when things aren't working out one way,  you shouldn't
continue to throw money at the problem and imagine things are going to
change.
    I know this is not much help--you really need a dentist who is willing
and able to get the best result possible for this.  If you are going to
a dentist who's answer as to what the magic bullet is that's going to
make everything right is the one word answer "implants"  it is highly
likely you need to make the acquaintance of another dentist.

Steve