While I believe that more parties, more participation and more diversity of political options is definitely a good thing. IMO the problem you are describing is not attributable to the lack of fourth or fifth PTI like 'pro-change' party, but simple electoral arithmetic and numbers. And actually another party will not fix these issues at all.
Let's look at the current state of affairs. Let's say the anti-old guard parties vote that PTI represents is something like 30-40% of the vote on average in each constituency, this is in line with PTI's national vote share in 2018 (32%). The rest is divided between PML, PPP, other regional parties, religious parties and independents and others. With a fourth and fifth party on Imran Khan's side, you will still only have that 30-40% of the vote to share between you. The key is to increase the share, not to have that share divided among more parties. Electorally this is a bad strategy.
Even worse, with our electoral system of First Past the Post (a system I've criticized in the past because it damages parties like PTI and favours parties like PPP and PML), with more parties on the ballot offering the same thing. You will just split the PTI vote and give them even fewer seats and less power.
E.g let's call your fourth party PTI-II, let's take NA x constituency where the results by party candidates were:
2018: PTI 35% (winner), PML 30%, PPP 20%, 15% other smaller parties and candidates.
With the FPTP system and another party just like PTI on the ballot the results might be this:
202x: PTI 25%, PML 30% (winner), PPP 20%, PTI-II 15%, 10% other parties.
With FPTP, the fourth PTI like party will only split the vote and make the opposition stronger. Even with a combined vote above 5% higher in the second scenario, the vote is split so you lose.
PTI supporters real problem isn't that there isn't a fourth party or that the opposition is united against them, although the latter is largely their doing. Their problems are that in NA, they are a minority government propped up by a coalition of old-guard parties like PMLQ and MQM, they also have a leadership problem that all Pakistani parties have to some extent. Another problem for PTI is that the current FPTP system is disadvantageous electorally to national parties like PTI in favour of regional stronghold parties, it's also defunct for the current political era. PTI are also too reliant on IK alone, if he goes, or retires in the future, a guy like SMQ is not going to inspire the support of voters as much. Lastly, opposition are emboldened further by the current dilapidated state of Pakistan's economy, criticism of the government really tends to stick when people are suffering, even if some of that suffering is not the fault of the government.
