Neil Lennon won loads of Scottish titles and I'm not sure how else you'd describe him
He might not be a completely shit manager but he's clearly woefully unambitious, and doesnt have much confidence in his ability. He's had one job which ended badly and instead of regrouping and starting again a little lower down, he's completely sold out to a retirement league.
His Scottish stint can be looked at two ways.
The good:
They were much improved in Europe during his time there
He won the league, stopping Celtic win 10 in a row
The bad:
He was there 4 seasons and won only one trophy. That's not good enough for Rangers, even if they were struggling when he took over. Although he left half way through his last season, Celtic had sorted themselves out and were back on top again
St Johnstone won both domestic cups the year Rangers won the league. His domestic cup record was particularly poor.
Celtic were woeful the season Rangers won it (in a 2 horse race) and it was the behind closed doors season.
Gerrard was on the brink of the sack when Covid kicked off and then the pause for lockdowns saved his job and then after the break they won the league the next year
By all accounts Mick Beale did all the tactical work (Villa fell to pieces after he left Villa for a manager job)
But his spell at Rangers didn't warrant a big Premier League job. He's done as a manager in England and his ego would never let him try and rebuild his reputation at a level that might get him a job (League One/League Two). Plus the salary would be miniscule compared to what he's on now.