The worst thing to come from that decade is the Class 142 Pacer units and the railway still suffers to this day from these horrendous units all because they wanted to save money instead of build more 156's.
Unfair that - they were designed for totally different uses.
The 'Pacers' were all designed for use on short urban runs or longer, light used branches.
The 155s / 156s were medium distance units.
The business case of extra 156s wouldn't have made sense, so if the Pacers hadn't happened you'd probably have seen service reductions or closures in an effort to extend the life further of some of the 1st generation units which were being withdrawn around that time.
The problem with the current use of the Pacers - as distinct to their original use - is a direct result of the growth the railways have seen in the last 20 years - and to be fair, few if any forecasts foresaw the growth the rail network has seen.